Hide merge commits from "changes since last review"

[asportnoy]

Like with the web view, changes from merge commits shouldn't be shown when viewing changes since the last review.

[seantleonard]

I would like to see this too. Whenever changes from main are merged into a current working branch, those changes then become noise within the view "Changes since last review." The PR Extension is unusable then. Because I don't want to use "review all changes" because I don't want to keep re-reviewing code changes I've already seen.