Add links to the API in documentation

[dannysperling]

No code changes - just documentation

[feiranchen]

Looks great! :star2: If we can have @see marks then we can update the https://github.com/octokit/go-octokit/blob/master/TODO.md list just like https://github.com/octokit/octokit.rb :+1: Elaborated here: https://github.com/octokit/go-octokit/pull/79

[dannysperling]

As per a discussion in person, @see notifications have been deemed unnecessary as they are ruby documentation. The TODO.md file should be able to be updated automatically without them.

[feiranchen]

:+1:

[pengwynn]

@dannysperling Looks like we have a merge conflict on this one. Need help resolving that?

[dannysperling]

@pengwynn Missed your comment earlier. I've fixed the conflicts and this endpoint should be ready to merge now.