surface related entities wherever maintainers spend their time

[tatianab]

Once we have an API for accessing related entities for a project (#22), it will be relatively easy to surface related entities in places other than issue trackers.

This is an umbrella issue to track work on surfacing related entities. Each location should get its own issue as we decide it is important and start work on it.

Some locations to consider:

• Code review (Gerrit)
• Chat (Google chat bot?)
• Go Forums
• IDE