Local-ized Links in PR and Issue Overviews

[Daniel-Aaron-Bloom]

Currently, editor-embedded comments with permalinks get replacePermalinked to make the links instead navigate to the local version of the file (with a view on GitHub backup). It would be nice if permalinks in PR/Issue descriptions and comments on the overview pages did the same.

Not only would this improve consistency, as currently clicking the same link in two different places has two different behaviors, but it also facilitates new workflows and usage patterns like having a TOC of PR file links in the sidebar and navigating through them as you review a PR.

Happy to help with an implementation if you agree this would be useful.

[Daniel-Aaron-Bloom]

Linking to #4569 since it was the inspiration for this