[+] add GHA workflow to build Docker image for each PR, closes #528

.github/workflows/build.yml

@@ -0,0 +1,34 @@
+name: Build & Test
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+
+  test-docker-images:
+    if: true # false to skip job during debug
+    name: Test Docker Image on Ubuntu
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Check out code
+      uses: actions/checkout@v3
+
+    - name: Version strings
+      id: version
+      run: |
+        echo "RELEASE_VERSION=$(echo "$GITHUB_REF_NAME#${GITHUB_SHA:0:6}")" >> $GITHUB_OUTPUT
+        echo "RELEASE_TIME=$(git show -s --format=%cI HEAD)" >> $GITHUB_OUTPUT
+
+    - name: Publish test version to Registry
+      uses: elgohr/Publish-Docker-Github-Action@v4
+      env:
+        GIT_HASH: ${{ steps.version.outputs.RELEASE_VERSION }}
+        GIT_TIME: ${{ steps.version.outputs.RELEASE_TIME }}     
+      with:
+        name: cybertec/pgwatch2-postgres
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+        dockerfile: docker/Dockerfile-postgres
+        buildargs: GIT_HASH,GIT_TIME
+        tags: ${{ github.ref_name }}