Add 'context: .' to fix 'not a git repository' error.

Author: brocaar

.github/workflows/main.yml

@@ -78,6 +78,7 @@ jobs:
         id: docker_build
         uses: docker/build-push-action@v2
         with:
+          context: .
           platforms: linux/amd64,linux/arm64
           push: ${{ startsWith(github.ref, 'refs/tags/v') }}
           tags: ${{ steps.meta.outputs.tags }}