actions: add new arm64 manifests

problem: new docker images are not pushed with combined manifests
solution: push manifests in github actions

Author: trws

.github/workflows/main.yml

@@ -254,4 +254,8 @@ jobs:
         echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin
         docker manifest create fluxrm/flux-core:bookworm fluxrm/flux-core:bookworm-amd64 fluxrm/flux-core:bookworm-386 fluxrm/flux-core:bookworm-arm64
         docker manifest push fluxrm/flux-core:bookworm
+        for d in el9 noble fedora40 ; do
+          docker manifest create fluxrm/flux-core:$d fluxrm/flux-core:$d-amd64 fluxrm/flux-core:$d-arm64
+          docker manifest push fluxrm/flux-core:$d
+        done