Add ARM64 builds (#108)

.github/workflows/publish-docker.yml

@@ -18,6 +18,11 @@ permissions:
   contents: read
   packages: write
 
+env:
+  platforms: linux/amd64,linux/arm64
+  registry: ghcr.io
+  image: ghcr.io/${{ github.repository_owner }}/fedhcp
+
 jobs:
   buildAndPush:
     runs-on: ubuntu-latest
@@ -29,7 +34,7 @@ jobs:
         id: meta
         with:
           images: |
-            ghcr.io/${{ github.repository_owner }}/fedhcp
+            ${{ env.image }}
           tags: |
             type=semver,pattern={{version}}
             type=schedule
@@ -57,15 +62,15 @@ jobs:
         if: github.event_name != 'pull_request'
         uses: docker/login-action@v3
         with:
-          registry: ghcr.io
+          registry: ${{ env.registry }}
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Build and push
         timeout-minutes: 40
         uses: docker/build-push-action@v5
         with:
           context: .
-          platforms: linux/amd64
+          platforms: ${{ env.platforms }}
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}