Githawk: Support GitHub comment editing history

[BasThomas]

You can see comment editing history on web now.
Taking a leap here but I think this is not available via the API yet, is it?

[Sherlouk]

Was about to create a new issue for this but GitHub's brand new "Related Issues" told me this existed 😆 Here are my notes, API now exists!

Is your feature request related to a problem? Please describe.
GitHawk currently supports displaying when a message has been edited but we can take this a step further by supporting GitHub's new comment history.

This can all be done with some additional GQL values on Issue and PullRequest nodes "userContentEdits":
https://developer.github.com/v4/object/usercontenteditconnection/

https://developer.github.com/v4/object/pullrequest/
https://developer.github.com/v4/object/issue/

Describe the solution you'd like
I believe we can just change the GQL query for loading an Issue/PR and pull in the edit information. I think we can take advantage of ContextMenu to show (in chronological order) the name of the person who changed it and the time they changed it. Tapping on an option can show a very simple page with the diff!

Describe alternatives you've considered
Exact UI I believe is up for debate but I believe using the GQL API is the most appropriate given our current setup for loading issues and PRs.

Additional context
Believe this is a rather low priority suggestion as the value of this could be disputed for many!