gh: publish image on ghcr.io

It looks like the Docker Hub and its mirrors are no longer available in
China, while ghrc.io seems OK for the moment.

It is easy to publish the image on ghcr.io as well, let's do that then.

Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

.github/workflows/dockerhub.yml

@@ -8,8 +8,14 @@ on:
 
 jobs:
   docker:
+    name: Build and push Docker images to multiple registries
     if: github.repository_owner == 'multipath-tcp'
     runs-on: ubuntu-latest
+    permissions:
+      packages: write
+      contents: read
+      attestations: write
+      id-token: write
     steps:
       -
         name: Set up QEMU
@@ -23,12 +29,21 @@ jobs:
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
+      -
+        name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
       -
         name: Build and push
         id: docker_build
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           platforms: linux/amd64,linux/arm64
           push: true
-          tags: mptcp/mptcp-upstream-virtme-docker:${{ github.ref_name }}
+          tags: |
+            mptcp/mptcp-upstream-virtme-docker:${{ github.ref_name }}
+            ghcr.io/${{ github.repository }}:${{ github.ref_name }}