feat(mr review): show change type for each changed file

Related to #276 (closed)

This description has been shamelessly pilfered from !196 (closed)

---

This MR is a Draft, till I add automated tests

The colorcoding on the "after" picture is:

• removed file: red and D character
• added file: green and A character
• renamed file: orange and R character
• modified file: default color and M character

before	after

How VS Code native source control sidebar indicates changes

Unfortunately, VS Code doesn't let us replicate the same experience. We use the FileDecoration and we can only set color of the whole line and we can't strike through.

Related to #276 (closed)