workflow: Add merge_group trigger to Build workflow

This should trigger the Build workflow when a merge group is created.

Signed-off-by: Gregers Gram Rygg <[email protected]>

.github/workflows/build.yml

@@ -37,6 +37,7 @@ on:
   push:
     branches:
       - main
+  merge_group:
   pull_request:
   schedule:
     - cron: "0 0 * * *"