Add workflow to push a development docker image (#392)

.github/workflows/push-dev-image.yml

@@ -0,0 +1,33 @@
+# This workflow can be used to push an image off a branch to Docker Hub.
+# This is useful to deploy changes to CB beta for testing.
+name: Push development image
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Docker Image Tag (Version)'
+        required: true
+        default: 'beta'
+
+jobs:
+  dev:
+      runs-on: ubuntu-latest
+
+      steps:
+      - uses: actions/checkout@v2
+
+      - name: Login to Docker Hub
+        run: echo ${{ secrets.DOCKER_HUB_PASSWORD }} | docker login -u ${{ secrets.DOCKER_HUB_USERNAME }} --password-stdin
+        continue-on-error: true
+
+      - uses: satackey/action-docker-layer-caching@v0.0.11
+        continue-on-error: true
+
+      - name: Build development image
+        run: |
+          docker build \
+            --tag metabrainz/critiquebrainz:"${{ github.event.inputs.tag }}" \
+            --build-arg GIT_COMMIT_SHA="${{ github.sha }}" .
+      - name: Push development image
+        run: docker push metabrainz/critiquebrainz:"${{ github.event.inputs.tag }}"