Update workflow.yml

.github/workflows/workflow.yml

@@ -16,6 +16,8 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
+      - name: Login to GitHub registry
+        run: docker login docker.pkg.github.com -u ${{ github.actor }} -p ${{ secrets.GITHUB_TOKEN }}
       - name: Build lowlighter/metrics:${{ github.head_ref || 'master' }}
         run: docker build -t lowlighter/metrics:${{ github.head_ref || 'master' }} .
       - name: Run tests