Add GitHub action to publish Docker image

.github/workflows/publish-docker.yml

@@ -0,0 +1,24 @@
+name: Publish Docker Image
+
+on:
+  push:
+    branches: ["main"]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Build the Docker image
+        working-directory: path
+        run: docker build . -t vincentbitter/koreader-calibre-web-sync:latest
+
+      - name: Log into Docker Hub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Push the images to Docker Hub
+        run: docker push vincentbitter/koreader-calibre-web-sync