setup action to build/publish on docker hub

.github/workflows/publish.yml

@@ -0,0 +1,29 @@
+name: Publish Docker image
+
+on:
+  push:
+    branches:
+      - 'master'
+      - 'devel'
+    tags:
+      - 'v*'
+
+jobs:
+  docker-hub:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: docker/metadata-action@v3
+        id: meta
+        with:
+          images: nim65s/matrix-webhook
+      - uses: docker/login-action@v1
+        with:
+          username: nim65s
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}