ci: add 'workflow_dispatch' trigger (#485)

* ci: add 'workflow_dispatch' trigger

* Update src/towncrier/newsfragments/485.misc

---------

Co-authored-by: Hynek Schlawack <[email protected]>

Author: umarcor

.github/workflows/ci.yml

@@ -5,6 +5,7 @@ on:
     branches: [ trunk ]
     tags: [ "**" ]
   pull_request:
+  workflow_dispatch:
 
 defaults:
   run: