Add link to browse source to README.md This makes it more clear to anyone landing directly at README.md instead of the root of the repo how to browse the source. Change-Id: I19b7e8e2f8e55385fa0825d4268623ef318bdaa0 Reviewed-on: https://chromium-review.googlesource.com/314441 Tested-by: Shannon Woods <shannonwoods@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>