Enable new [range-diff] feature in triagebot

Author: Urgau

triagebot.toml

@@ -1589,3 +1589,8 @@ days-threshold = 28
 # Documentation at: https://forge.rust-lang.org/triagebot/concern.html
 [concern]
 labels = ["S-waiting-on-concerns"]
+
+# Enable comments linking to triagebot range-diff when a PR is rebased
+# onto a different base commit
+# Documentation at: https://forge.rust-lang.org/triagebot/range-diff.html
+[range-diff]