ci: tag release container images

.github/workflows/build-container.yml

@@ -1,8 +1,11 @@
 name: Update Docker image
+
 on:
   push:
     branches:
       - master
+    tags:
+      - '*'  # This triggers the action on all tag pushes
 
 jobs:
   publish-docker-image:
@@ -13,13 +16,22 @@ jobs:
     steps:
       - name: Checkout repo
         uses: actions/checkout@v4
+
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v3
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
-      - name: Build and push Docker image to the GHCR
+
+      - name: Build and push the master container image
         run: |
           docker build . --tag ghcr.io/gbdev/rgbds:master
           docker push ghcr.io/gbdev/rgbds:master
+        
+      - name: Tag release container image
+        if: startsWith(github.ref, 'refs/tags/')
+        run: |
+          TAG_NAME=${GITHUB_REF#refs/tags/}
+          docker tag ghcr.io/gbdev/rgbds:master ghcr.io/gbdev/rgbds:$TAG_NAME
+          docker push ghcr.io/gbdev/rgbds:$TAG_NAME