triagebot: enable PR review status flipping and its shortcuts

Author: jieyouxu

src/doc/rustc-dev-guide/triagebot.toml

@@ -10,6 +10,25 @@ exclude_labels = [
     "C-tracking-issue",
 ]
 
+[review-submitted]
+# This label is added when a "request changes" review is submitted.
+reviewed_label = "S-waiting-on-author"
+# These labels are removed when a "request changes" review is submitted.
+review_labels = ["S-waiting-on-review"]
+
+[review-requested]
+# Those labels are removed when PR author requests a review from an assignee
+remove_labels = ["S-waiting-on-author"]
+# Those labels are added when PR author requests a review from an assignee
+add_labels = ["S-waiting-on-review"]
+
+# Enable tracking of PR review assignment
+# Documentation at: https://forge.rust-lang.org/triagebot/pr-assignment-tracking.html
+[shortcut]
+
+[autolabel."S-waiting-on-review"]
+new_pr = true
+
 [relabel]
 allow-unauthenticated = [
     "-Z*",