No comments in the editor when visiting file changes from commits

[rebornix]

• VSCode version: 1aab8e140e17f30a60b95df32264a39eb155765d
• Extension version: 0.0.7

Reproduce steps:

• Checkout Pull Request from the tree view Hook up webflow auth during credential checks #94
• Expand Commits node from Changes In Pull Request section
• Expand Commit "Tweak the authentication user messages"
• One file change src/github/credentials is shown and it has a comment icon
• Click the file change, a diff editor is opened. No comment is shown in the editor

[rebornix]

A DocumentCommentsProvider should be registered when visiting commits which have comments.

[rebornix]

As there is no comments, we don't see commenting range decorations as well.

[alexr00]

Viewing comments works, but adding them still does not.

[alexr00]

Adding comments is a duplicate of the more popular #2793