[Enhancement]: Refactor circleCI config

[nataliemarleny]

[Suggested Enhancement] This PR does a couple of refactors for ./.cicleci/config.yml to improve readability.

86e71d4

• Split long commands into multiple lines for easier readability.

5db39db

• Use parameter to de-duplicate circleCI commands (could see there was some duplication with browser tests)
• Reference for usage of parameters within the circleCI command: https://circleci.com/docs/2.0/configuration-reference/#commands-requires-version-21

[github-actions]

Stats from current PR

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	zeit/next.js canary	nataliemarleny/next.js enhancement-circleCI	Change
Build Duration	15s	14.8s	-210ms
node_modules Size	45.4 MB	45.4 MB	⚠️ +40 B
Total Bundle (main, webpack, commons) Size	210 kB	210 kB	✓
Total Bundle (main, webpack, commons) gzip Size	68.8 kB	68.8 kB	✓
Client _app Size	2.39 kB	2.39 kB	✓
Client _app gzip Size	1.08 kB	1.08 kB	✓
Client _error Size	8.45 kB	8.45 kB	✓
Client _error gzip Size	3.24 kB	3.24 kB	✓
Client pages/index Size	296 B	296 B	✓
Client pages/index gzip Size	222 B	222 B	✓
Client pages/link Size	4.14 kB	4.14 kB	✓
Client pages/link gzip Size	1.82 kB	1.82 kB	✓
Client pages/routerDirect Size	423 B	423 B	✓
Client pages/routerDirect gzip Size	306 B	306 B	✓
Client pages/withRouter Size	435 B	435 B	✓
Client pages/withRouter gzip Size	301 B	301 B	✓
Client main Size	23.7 kB	23.7 kB	✓
Client main gzip Size	7.81 kB	7.81 kB	✓
Client commons Size	184 kB	184 kB	✓
Client commons gzip Size	59.7 kB	59.7 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	770 B	770 B	✓
Base Rendered Size	1.36 kB	1.36 kB	✓
Build Dir Size	756 kB	756 kB	✓

Click to expand serverless stats

	zeit/next.js canary	nataliemarleny/next.js enhancement-circleCI	Change
Build Duration	15.5s	15.8s	⚠️ +260ms
node_modules Size	45.4 MB	45.4 MB	⚠️ +40 B
Total Bundle (main, webpack, commons) Size	210 kB	210 kB	✓
Total Bundle (main, webpack, commons) gzip Size	68.8 kB	68.8 kB	✓
Client _app Size	2.39 kB	2.39 kB	✓
Client _app gzip Size	1.08 kB	1.08 kB	✓
Client _error Size	8.45 kB	8.45 kB	✓
Client _error gzip Size	3.24 kB	3.24 kB	✓
Client pages/index Size	296 B	296 B	✓
Client pages/index gzip Size	222 B	222 B	✓
Client pages/link Size	4.14 kB	4.14 kB	✓
Client pages/link gzip Size	1.82 kB	1.82 kB	✓
Client pages/routerDirect Size	423 B	423 B	✓
Client pages/routerDirect gzip Size	306 B	306 B	✓
Client pages/withRouter Size	435 B	435 B	✓
Client pages/withRouter gzip Size	301 B	301 B	✓
Client main Size	23.7 kB	23.7 kB	✓
Client main gzip Size	7.81 kB	7.81 kB	✓
Client commons Size	184 kB	184 kB	✓
Client commons gzip Size	59.7 kB	59.7 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	770 B	770 B	✓
Serverless pages/link Size	338 kB	338 kB	✓
Serverless pages/link gzip Size	86.7 kB	86.7 kB	✓
Serverless pages/index Size	Error getting size	Error getting size	✓
Serverless pages/index gzip Size	Error getting size	Error getting size	✓
Serverless pages/_error Size	328 kB	328 kB	✓
Serverless pages/_error gzip Size	84 kB	84 kB	✓
Serverless pages/routerDirect Size	329 kB	329 kB	✓
Serverless pages/routerDirect gzip Size	84.3 kB	84.3 kB	⚠️ +1 B
Serverless pages/withRouter Size	329 kB	329 kB	✓
Serverless pages/withRouter gzip Size	84.3 kB	84.3 kB	⚠️ +1 B
Build Dir Size	1.94 MB	1.94 MB	✓

[github-actions]

Stats from current PR

Click to expand stats

	zeit/next.js canary	nataliemarleny/next.js enhancement-circleCI	Change
Build Duration	13.5s	13.4s	-45ms
node_modules Size	45.4 MB	45.4 MB	⚠️ +40 B
Total Bundle (main, webpack, commons) Size	210 kB	210 kB	✓
Total Bundle (main, webpack, commons) gzip Size	68.8 kB	68.8 kB	✓
Client _app Size	2.39 kB	2.39 kB	✓
Client _app gzip Size	1.08 kB	1.08 kB	✓
Client _error Size	8.45 kB	8.45 kB	✓
Client _error gzip Size	3.24 kB	3.24 kB	✓
Client pages/index Size	296 B	296 B	✓
Client pages/index gzip Size	222 B	222 B	✓
Client pages/link Size	4.14 kB	4.14 kB	✓
Client pages/link gzip Size	1.82 kB	1.82 kB	✓
Client pages/routerDirect Size	423 B	423 B	✓
Client pages/routerDirect gzip Size	306 B	306 B	✓
Client pages/withRouter Size	435 B	435 B	✓
Client pages/withRouter gzip Size	301 B	301 B	✓
Client main Size	23.7 kB	23.7 kB	✓
Client main gzip Size	7.81 kB	7.81 kB	✓
Client commons Size	184 kB	184 kB	✓
Client commons gzip Size	59.7 kB	59.7 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	770 B	770 B	✓
Base Rendered Size	1.36 kB	1.36 kB	✓
Build Dir Size	756 kB	756 kB	✓

Click to expand serverless stats

	zeit/next.js canary	nataliemarleny/next.js enhancement-circleCI	Change
Build Duration	14.4s	13.9s	-456ms
node_modules Size	45.4 MB	45.4 MB	⚠️ +40 B
Total Bundle (main, webpack, commons) Size	210 kB	210 kB	✓
Total Bundle (main, webpack, commons) gzip Size	68.8 kB	68.8 kB	✓
Client _app Size	2.39 kB	2.39 kB	✓
Client _app gzip Size	1.08 kB	1.08 kB	✓
Client _error Size	8.45 kB	8.45 kB	✓
Client _error gzip Size	3.24 kB	3.24 kB	✓
Client pages/index Size	296 B	296 B	✓
Client pages/index gzip Size	222 B	222 B	✓
Client pages/link Size	4.14 kB	4.14 kB	✓
Client pages/link gzip Size	1.82 kB	1.82 kB	✓
Client pages/routerDirect Size	423 B	423 B	✓
Client pages/routerDirect gzip Size	306 B	306 B	✓
Client pages/withRouter Size	435 B	435 B	✓
Client pages/withRouter gzip Size	301 B	301 B	✓
Client main Size	23.7 kB	23.7 kB	✓
Client main gzip Size	7.81 kB	7.81 kB	✓
Client commons Size	184 kB	184 kB	✓
Client commons gzip Size	59.7 kB	59.7 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	770 B	770 B	✓
Serverless pages/link Size	338 kB	338 kB	✓
Serverless pages/link gzip Size	86.7 kB	86.7 kB	⚠️ +1 B
Serverless pages/index Size	Error getting size	Error getting size	✓
Serverless pages/index gzip Size	Error getting size	Error getting size	✓
Serverless pages/_error Size	328 kB	328 kB	✓
Serverless pages/_error gzip Size	84 kB	84 kB	⚠️ +1 B
Serverless pages/routerDirect Size	329 kB	329 kB	✓
Serverless pages/routerDirect gzip Size	84.3 kB	84.3 kB	✓
Serverless pages/withRouter Size	329 kB	329 kB	✓
Serverless pages/withRouter gzip Size	84.3 kB	84.3 kB	⚠️ +1 B
Build Dir Size	1.94 MB	1.94 MB	✓