Support patch comments inline with code

[gsaslis]

In order to support a better code review experience, it is useful to add inline comments and start threads on specific lines, focusing the discussion around specific code changes.

This is made possible by clicking a '+' or 💬 next to a line (only for lines that have changed in the Patch), as can be seen also in the screenshot below from the gitlab workflow extension.

I am also including a screenshot from the github extension, but that includes additional functionality we don't want to add at this point in time