feat: add GHCR as a registry

Author: joedwards32

.github/workflows/docker-publish.yml

@@ -46,13 +46,24 @@ jobs:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
 
-      # Extract metadata (tags, labels) for Docker
+      # Login to GitHub Container Registry
+      - name: Log in to GHCR
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@f4ef78c080cd8ba55a85445d5b36e214a81df20a
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Extract metadata (tags, labels) for both registires
       # https://github.com/docker/metadata-action
       - name: Extract Docker metadata
         id: meta
         uses: docker/metadata-action@96383f45573cb7f253c731d3b3ab81c87ef81934 # v5.0.0
         with:
-          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          images: |
+            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+            ${{ env.GHCR_REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
             type=raw,value=latest,enable={{is_default_branch}}
             type=semver,pattern={{version}}