Add multi-platform builds

Author: ezhlobo

.github/workflows/release-image.yml

@@ -34,8 +34,9 @@ jobs:
         with:
           context: ./image
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: |
             ghcr.io/${{ github.repository_owner }}/devcontainer:latest
-            ghcr.io/${{ github.repository_owner }}/devcontainer:${{ github.sha }}
+            ghcr.io/${{ github.repository_owner }}/devcontainer:sha-${{ github.sha }}
           cache-from: type=gha
           cache-to: type=gha,mode=max