add 3.13 as an option on the bug form (python#111083)

Author: nedbat

.github/ISSUE_TEMPLATE/bug.yml

@@ -39,6 +39,7 @@ body:
         - "3.10"
         - "3.11"
         - "3.12"
+        - "3.13"
         - "CPython main branch"
     validations:
       required: true