Change docs links to actual file extension (.md)

See https://gerrit-review.googlesource.com/83950 for detailed context.

Change-Id: I674c1f6eab6ed28956fbb685c83c88f87ac015f5
1 file changed
tree: 5a9225b06f92fdf6005758dc2645f195114ca19a
  1. .buckconfig
  2. .gitignore
  3. BUCK
  4. lib/
  5. src/