Docs: update release steps

[humitos]

We have our release process explained at

https://readthedocs-client.readthedocs.io/en/latest/releasing.html

However, with the introduction of wrangler in the community/corporate repositories via common/ submodule, we now require also:

1. update NGINX_ADDONS_GITHUB_TAG: https://github.com/readthedocs/common/blob/main/dockerfiles/docker-compose.yml#L29
2. update common/ submodule on community and commercial as well

To solve 2) in a more generic way, it would be good if we can make common/ submodule to always point to the latest commit in main branch. cc @stsewd do you know if this is possible?

[stsewd]

it would be good if we can make common/ submodule to always point to the latest commit in main branch. cc @stsewd do you know if this is possible?

I don't think so.