setup.md: Document external requirements

Solves: Jira GER-2365
Change-Id: Ibbc6d45a7d01a92df6b17d2272f47f8eb08e6654
1 file changed
tree: 540e65d92f0c56e06a4234a75b4979cc034a921a
  1. src/
  2. BUILD
  3. external_plugin_deps.bzl