Add workflow_dispatch trigger to build workflow

Author: matejbart

.github/workflows/build.yml

@@ -4,7 +4,7 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
-on: [push, pull_request]
+on: [push, pull_request, workflow_dispatch]
 
 defaults:
   run: