Rollup merge of rust-lang#143695 - Urgau:waiting-on-author-new_draft, r=Kobzol

Auto-add `S-waiting-on-author` when the PR is/switches to draft state

This PR adds the `S-waiting-on-author` as a `new_draft` when the PR is/switches to draft state.

Related to rust-lang/triagebot#2102 & rust-lang/triagebot#2104

cc `@jieyouxu`
r? `@Kobzol`

Author: matthiaskrgr

triagebot.toml

@@ -535,6 +535,9 @@ trigger_files = [
 [autolabel."S-waiting-on-review"]
 new_pr = true
 
+[autolabel."S-waiting-on-author"]
+new_draft = true
+
 [autolabel."needs-triage"]
 new_issue = true
 exclude_labels = [