Add docker builds on tags

.github/workflows/docker.yml

@@ -4,6 +4,11 @@ on:
   push:
     branches:
       - 'master'
+    tags:
+      - 'v*'
+  pull_request:
+    branches:
+      - 'master'
 
 jobs:
   docker:
@@ -18,9 +23,23 @@ jobs:
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
+      -
+        name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: 42wim/matterbridge
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=semver,pattern={{version}}
+            type=semver,pattern=stable
+            type=semver,pattern={{major}}
+            type=semver,pattern={{major}}.{{minor}}
       -
         name: Login to DockerHub
         uses: docker/login-action@v1 
+		if: github.event_name != 'pull_request'
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
@@ -30,6 +49,7 @@ jobs:
         uses: docker/build-push-action@v2
         with:
           context: .
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
-          tags: 42wim/matterbridge:latest
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}