Rollup merge of rust-lang#145674 - Urgau:triagebot-review-changes-since, r=Kobzol

Enable triagebot `[review-changes-since]` feature

This PR enables triagebot [`[review-changes-since]` feature](https://forge.rust-lang.org/triagebot/review-changes-since.html).

It's a complement to triagebot `[range-diff]` feature which adds at the end of a review body a link to view the changes that happened since the review.

Asked in [#t-compiler > Experimental range-diff for force-push @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Experimental.20range-diff.20for.20force-push/near/534963522)

r? Kobzol

Author: jhpratt

triagebot.toml

@@ -1603,3 +1603,8 @@ labels = ["S-waiting-on-concerns"]
 # onto a different base commit
 # Documentation at: https://forge.rust-lang.org/triagebot/range-diff.html
 [range-diff]
+
+# Adds at the end of a review body a link to view the changes that happened
+# since the review
+# Documentation at: https://forge.rust-lang.org/triagebot/review-changes-since.html
+[review-changes-since]