feat: support GitHub's improved pull request "Files Changed" experience

[jkowalleck]

GitHub is revisiting their view for PullRequest's "Files Changes" feature, including the file tree.
see https://github.com/orgs/community/discussions/163932

⚠️ the new github feature is still in preview (not final).

The current file tree is properly supported by this browser extension:

• see screenshot:
  

The upcoming/revisited one is not entirely supported by this browser extension, yet:

• folder icons are working as intended
• file icons are not working as intended
• see screenshot:
  

[PKief]

Thanks for bringing this up, I also just noticed that it's not working anymore with the files in my browser. However, maybe it's better to wait until they officially roll that feature out, otherwise we'll have some additional work and adjust some code, which is likely to be changed later. As we still support the non-preview version of the file diff in Github we're still good. Let's give this some time and then we will decide how to improve this feature.