Secure pass GITHUB_TOKEN to action

Author: martenrichter

.github/workflows/docker-image.yml

@@ -15,4 +15,4 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Build the Docker image
-      run: docker build . --file Dockerfile --build-arg GH_TOKEN=${{ secrets.GITHUB_TOKEN }} --tag ghcr.io/fails-components/notepadhandler:$(date +%s)
+      run: export GH_TOKEN=${{ secrets.GITHUB_TOKEN }}; docker build . --file Dockerfile --secret id=GH_TOKEN  --tag ghcr.io/fails-components/notepadhandler:$(date +%s)