Merge public/common docs with the blink/public ones

Move //third_party/blink/public/common/README.md into
//third_party/blink/public/README.md, putting it together with the
public/web and public/platform documentation.

Bug: None
Change-Id: I560e1c419939ae026f1704d0b1fa0597069cfb95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2007746
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Henrique Ferreiro <hferreiro@igalia.com>
Cr-Commit-Position: refs/heads/master@{#733325}
2 files changed