added docker image support

* added environment variable support
* added docker instructions
* added .env hint

.github/workflows/pushimage.yaml

@@ -0,0 +1,28 @@
+name: build-push-image
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  build-and-push-image:
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
+        with:
+          registry: https://ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
+        with:
+          push: true
+          tags: ghcr.io/tlinden/kleingebaeck:${{ github.ref_name}}