ci: add workflow to publish runner image to docker hub

.gitea/workflows/publish-runner.yml

@@ -0,0 +1,39 @@
+name: Publish Runner Image
+
+on:
+  push:
+    paths:
+      - 'docker/runner/**'
+      - '.gitea/workflows/publish-runner.yml'
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  push_to_registry:
+    name: Push Docker image to Docker Hub
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v3
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v4
+        with:
+          context: ./docker/runner
+          file: ./docker/runner/Dockerfile
+          push: true
+          tags: ${{ secrets.DOCKER_USERNAME }}/vibetorrent-runner:latest
+          platforms: linux/amd64,linux/arm64