feat: multi-platform container build

Signed-off-by: Leonardo Cecchi <[email protected]>

Author: leonardoce

.github/workflows/build-containers.yml

@@ -29,4 +29,5 @@ jobs:
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6
         with:
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: ${{ env.REGISTRY }}/cloudnative-pg/docs:latest