Add more detail to developer "Publishing new releases" docs

[adamltyson]

Include more detail for new devs, including:

• Developer who creates a new feature is usually the one to release the version if required
• What exactly we mean by the semantic version numbering
• When/where/how new features should be advertised (blog, discussions, zulip, slack etc)

When things get released could be:

• Release the package if the changes are useful to users
• Update the metapackage if the changes are important to new users (new versions should be downloaded anyway, updating the metapackage forces it)
• Update workflows if the changes are relevant to a workflow

cc @alessandrofelder