Build image on pull request

Author: jovial

.github/workflows/build-docker.yml

@@ -2,6 +2,7 @@
 
 name: Docker Build & Publish to GitHub Container Registry
 on:
+  pull_request:
   push:
     branches:
       - 'main'
@@ -40,9 +41,9 @@ jobs:
       - name: Build and Push Latest Docker Image
         id: build-and-push-latest
         uses: docker/build-push-action@v2
-        if: ${{ github.ref == 'refs/heads/main' }}
+        if: ${{ github.ref_type == 'branch' }}
         with:
           context: .
-          push: true
+          push: ${{ github.ref == 'refs/heads/main' }}
           tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
           labels: ${{ steps.meta.outputs.labels }}