docs: Updated CONTRIBUTING.md with some rough notes for managing docker

CONTRIBUTING.md

@@ -75,8 +75,22 @@ To release a new version:
 * `git tag -a vN.N.N -m 'vN.N.N'`
 * `git tag -f latest`
 * `git push --tags`
-* This should then run a "hcltm release" action to release a new version
-* From this repo, you need to push the new docker container (`VERSION=N.N.N TAG=latest make imagepush`) - this may take a while :grimace:
+* This should then run a "hcltm release" action to release a new version, including amd64/arm64 docker images to ghcr.io
+* The following step is now redundant:
+** From this repo, you need to push the new docker container (`VERSION=N.N.N TAG=latest make imagepush`) - this may take a while :grimace:
+* From the https://github.com/xntrik/hcltm/pkgs/container/hcltm page, docker pull the two architectures locally
+* You then need to re-tag them for docker.io:
+** docker tag [imageid-arm64] xntrik/hcltm:latest
+** docker push xntrik/hcltm:latest
+** docker tag [imageid-arm64] xntrik/hcltm-arm64:latest
+** docker push xntrik/hcltm-arm64:latest
+** docker tag [imageid-amd64] xntrik/hcltm-amd64:latest
+** docker push xntrik/hcltm-amd64:latest
+** docker manifest create xntrik/hcltm:latest xntrik/hcltm-arm64:latest xntrik/hcltm-amd64:latest
+** docker manifest annotate xntrik/hcltm:latest xntrik/hcltm-arm64:latest --arch arm64
+** docker manifest annotate xntrik/hcltm:latest xntrik/hcltm-amd64:latest --arch amd64
+** docker manifest push xntrik/hcltm:latest
+** Check that the "latest" tag includes both architectures, then, repeat the above and use the new version instead of "latest"
 * Then don't forget to update https://github.com/xntrik/homebrew-repo
 * And also https://github.com/xntrik/hcltm-action and https://github.com/xntrik/hcltm-action-example