Native views: Allow reading, commenting and editing issues & prs inside the app

[brunolemos]

The primary goal is to increase user productivity, so it can do everything inside the app instead of opening a new browser tab. Open an issue, close, add/remove labels, assign, read comments, leave a comment, etc.

The secondary goal is Growth Hacking. GitHub will show the app name on each comment, which will probably make more users discover the app: