Add the githash to docker builds

.github/workflows/docker.yml

@@ -9,6 +9,9 @@ jobs:
   docker:
     runs-on: ubuntu-latest
     steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
       -
         name: Set up QEMU
         uses: docker/setup-qemu-action@v1
@@ -26,6 +29,7 @@ jobs:
         id: docker_build
         uses: docker/build-push-action@v2
         with:
+          context: .
           push: true
           tags: 42wim/matterbridge:latest