Add github action docker build and use github docker registry

Author: baluchicken

.github/workflows/docker.yml

@@ -0,0 +1,24 @@
+name: Docker
+on:
+  push:
+    branches:
+      - master
+    tags:
+      - "^v?[0-9]+.[0-9]+.[0-9]+"
+jobs:
+  docker:
+    name: Docker
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Build kafka-operator
+        uses: docker/build-push-action@v1
+        with:
+          username: ${{ github.actor }}
+          password: ${{ secrets.CR_PAT }}
+          registry: ghcr.io
+          repository: banzaicloud/kafka-operator
+          dockerfile: Dockerfile
+          tag_with_ref: true
+          add_git_labels: true