Allow manual trigger for Github CI (#2022)

Summary:
Pull Request resolved: #2022

Allow triggering a Github CI job manually instead of only on pull requests + push.
This way we can retry at any given commit easily.

Reviewed By: pzhan9

Differential Revision: D88086665

fbshipit-source-id: b4c6cbba26e2872e9a7ff017011897a3a7eaea60

Author: dulinriley

.github/workflows/ci.yml

@@ -8,6 +8,7 @@ on:
   push:
     branches:
       - main
+  workflow_dispatch: # Allows manual triggering
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref == 'refs/heads/main' && github.run_number || github.ref }}