Merge pull request #4 from ESPresense/ci/enable-pr-builds

ci: enable Docker builds on PRs

Author: DTTerastar

.github/workflows/docker.yml

@@ -3,6 +3,8 @@ on:
   push:
     branches: [main]
     tags: ['v*']
+  pull_request:
+    branches: [main]
 
 jobs:
   build-and-push:
@@ -33,12 +35,13 @@ jobs:
             type=semver,pattern={{major}}
             type=sha,prefix=sha-
             type=raw,value=latest,enable={{is_default_branch}}
+            type=ref,event=pr
 
       - name: Build and push
         uses: docker/build-push-action@v6
         with:
           context: .
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha