Merge branch 'master' into v2

* master: (219 commits)
  Revert "Add rawMarkdownBody to node.internal" (gatsbyjs#5769)
  Publish
  Change code highlights to the correct lines (gatsbyjs#5765)
  Update sitemap example to include posts and exclude sample page (gatsbyjs#5723)
  [gatsby-transformer-remark] add rawMarkdownBody  (gatsbyjs#5557)
  [gatsby-image] add placeholderStyle prop (gatsbyjs#5745)
  [gatsby-plugin-sharp] toFormat fix and unify defaultArgs handling (gatsbyjs#5071)
  [gatsby-source-wordpress] Do not assume entities will exist (gatsbyjs#5004)
  [gatsby-transformer-excel] add option to disable raw output (gatsbyjs#5746)
  Update gatsby-config.js (gatsbyjs#5744)
  Publish
  [gatsby-source-mongodb] Use Promises to prevent calling done too early (gatsbyjs#5738)
  clues about this being advanced
  [gatsby-source-wordpress] Treat wp settings as a known type for inclusion (gatsbyjs#5708)
  [www] Add dot com to main navigation (gatsbyjs#5579)
  Publish
  fixed TOC links, shortened TOC, localhost edits
  Introduction to Gatsby blog post (gatsbyjs#5628)
  Update gatsby-config.js (gatsbyjs#5688)
  Add envinfo to gatsby-cli, issue template (gatsbyjs#5594)
  ...

# Conflicts:
#	.github/ISSUE_TEMPLATE/bug_report.md
#	.github/ISSUE_TEMPLATE/question.md
#	README.md
#	docs/blog/author.yaml
#	docs/docs/adding-search.md
#	docs/docs/gatsby-starters.md
#	docs/docs/how-to-contribute.md
#	docs/docs/image-tutorial.md
#	docs/docs/source-plugin-tutorial.md
#	docs/docs/wordpress-source-plugin-tutorial.md
#	docs/docs/working-with-images.md
#	docs/tutorial/part-two/index.md
#	examples/image-processing/src/pages/index.js
#	examples/sitemap/gatsby-node.js
#	examples/sitemap/src/pages/index.js
#	examples/sitemap/src/pages/page-2.js
#	examples/sitemap/src/pages/secret.js
#	examples/using-asciidoc/.eslintrc
#	examples/using-contentful/.eslintrc
#	examples/using-contentful/.eslintrc.json
#	examples/using-css-modules/.eslintrc
#	examples/using-css-modules/.eslintrc.json
#	examples/using-csv/.eslintrc
#	examples/using-csv/.eslintrc.json
#	examples/using-drupal/.eslintrc
#	examples/using-drupal/.eslintrc.json
#	examples/using-emotion/.eslintrc
#	examples/using-emotion/.eslintrc.json
#	examples/using-excel/.eslintrc
#	examples/using-excel/.eslintrc.json
#	examples/using-gatsby-image/.eslintrc
#	examples/using-gatsby-image/.eslintrc.json
#	examples/using-glamor/.eslintrc
#	examples/using-glamor/.eslintrc.json
#	examples/using-hjson/.eslintrc
#	examples/using-hjson/.eslintrc.json
#	examples/using-mongodb/.eslintrc
#	examples/using-mongodb/.eslintrc.json
#	examples/using-page-loading-indicator/.eslintrc
#	examples/using-page-loading-indicator/.eslintrc.json
#	examples/using-path-prefix/.eslintrc
#	examples/using-path-prefix/.eslintrc.json
#	examples/using-react-native-web/.eslintrc
#	examples/using-react-native-web/.eslintrc.json
#	examples/using-react-url-query/.eslintrc
#	examples/using-react-url-query/.eslintrc.json
#	examples/using-redirects/.eslintrc
#	examples/using-redirects/.eslintrc.json
#	examples/using-remark-copy-linked-files/.eslintrc
#	examples/using-remark-copy-linked-files/.eslintrc.json
#	examples/using-sqip/src/components/polaroid.js
#	examples/using-sqip/src/layouts/index.js
#	examples/using-styled-components/.eslintrc
#	examples/using-styled-components/.eslintrc.json
#	examples/using-styled-jsx/.eslintrc
#	examples/using-styled-jsx/.eslintrc.json
#	examples/using-styletron/.eslintrc
#	examples/using-styletron/.eslintrc.json
#	examples/using-wordpress/gatsby-node.js
#	packages/gatsby-cli/package.json
#	packages/gatsby-image/package.json
#	packages/gatsby-image/src/index.js
#	packages/gatsby-link/package.json
#	packages/gatsby-plugin-catch-links/package.json
#	packages/gatsby-plugin-emotion/README.md
#	packages/gatsby-plugin-emotion/package.json
#	packages/gatsby-plugin-emotion/src/gatsby-node.js
#	packages/gatsby-plugin-feed/package.json
#	packages/gatsby-plugin-google-tagmanager/package.json
#	packages/gatsby-plugin-manifest/package.json
#	packages/gatsby-plugin-netlify/package.json
#	packages/gatsby-plugin-offline/package.json
#	packages/gatsby-plugin-postcss-sass/package.json
#	packages/gatsby-plugin-postcss-sass/src/__tests__/gatsby-node.js
#	packages/gatsby-plugin-postcss-sass/src/gatsby-node.js
#	packages/gatsby-plugin-sharp/package.json
#	packages/gatsby-plugin-sharp/src/index.js
#	packages/gatsby-plugin-sitemap/package.json
#	packages/gatsby-plugin-styletron/package.json
#	packages/gatsby-plugin-stylus/package.json
#	packages/gatsby-plugin-stylus/src/__tests__/gatsby-node.js
#	packages/gatsby-react-router-scroll/package.json
#	packages/gatsby-remark-autolink-headers/package.json
#	packages/gatsby-remark-copy-linked-files/package.json
#	packages/gatsby-remark-embed-snippet/package.json
#	packages/gatsby-remark-images/package.json
#	packages/gatsby-remark-katex/package.json
#	packages/gatsby-remark-prismjs/package.json
#	packages/gatsby-remark-responsive-iframe/package.json
#	packages/gatsby-source-contentful/package.json
#	packages/gatsby-source-contentful/src/gatsby-node.js
#	packages/gatsby-source-contentful/src/normalize.js
#	packages/gatsby-source-drupal/package.json
#	packages/gatsby-source-faker/package.json
#	packages/gatsby-source-filesystem/package.json
#	packages/gatsby-source-mongodb/package.json
#	packages/gatsby-source-mongodb/src/gatsby-node.js
#	packages/gatsby-source-wordpress/package.json
#	packages/gatsby-transformer-excel/package.json
#	packages/gatsby-transformer-json/README.md
#	packages/gatsby-transformer-json/package.json
#	packages/gatsby-transformer-remark/package.json
#	packages/gatsby-transformer-screenshot/package.json
#	packages/gatsby-transformer-sharp/package.json
#	packages/gatsby-transformer-sharp/src/extend-node-type.js
#	packages/gatsby-transformer-sharp/src/types.js
#	packages/gatsby-transformer-sqip/.babelrc
#	packages/gatsby-transformer-sqip/package.json
#	packages/gatsby-transformer-sqip/src/extend-node-type.js
#	packages/gatsby-transformer-yaml/package.json
#	packages/gatsby/cache-dir/static-entry.js
#	packages/gatsby/package.json
#	packages/gatsby/src/cache-dir/app.js
#	packages/gatsby/src/cache-dir/production-app.js
#	packages/gatsby/src/internal-plugins/query-runner/query-runner.js
#	packages/gatsby/src/schema/__tests__/data-tree-utils-test.js
#	packages/gatsby/src/schema/type-conflict-reporter.js
#	packages/gatsby/src/utils/api-browser-docs.js
#	packages/gatsby/src/utils/api-node-docs.js
#	packages/gatsby/src/utils/webpack.config.js
#	www/gatsby-config.js
#	www/package.json
#	www/src/components/masthead.js
#	www/src/data/sidebars/doc-links.yaml
#	www/src/data/sites.yml
#	www/src/layouts/index.js
#	www/src/pages/blog/index.js
#	www/src/pages/plugins.js
#	yarn.lock