refactor(dev-infra): allow use-case and confusing types to be marked as 'triaged' (#38081)

Some issue reports don't really fall into any of the current buckets that count
towards triage level 2: bug/fix, feature, or refactor. Some reports are:
* working as intended but confusing - the labels might be 'type: confusing', 'comp: docs', 'comp: router'
* generally working as originally designed but a use-case could be argued for a different implementation.
 This type of report is a little hard to triage; it may be neither a bug, nor feature but more of a
 'type: use-case'. These may eventually turn into a bug/fix or feature, but can't necessarily be
 put in those buckets immediately.

PR Close #38081

.github/angular-robot.yml

@@ -154,6 +154,12 @@ triage:
     -
       - "type: RFC / Discussion / question"
       - "comp: *"
+    -
+      - "type: confusing"
+      - "comp: *"
+    -
+      - "type: use-case"
+      - "comp: *"
 
 # options for the triage PR plugin
 triagePR: