Initial import of JetStream v2.1

Upstream source: https://github.com/WebKit/WebKit/tree/main/Websites/browserbench.org/JetStream2.1

- Add webkit LICENSE file
- Add README.md

Bug: 340983089
Change-Id: I9f5955c27c063eb051c24ccec1fc3ddf4e83e479
Reviewed-on: https://chromium-review.googlesource.com/c/external/github.com/WebKit/JetStream/+/5548275
Reviewed-by: John Chen <johnchen@chromium.org>
484 files changed