docs: add a how-to guide about publishing a charm

[dwilding]

This PR adds a how-to guide to fill a gap in the Ops docs: We talk about how make a charm discoverable on Charmhub, but not how to publish to Charmhub in the first place. I want to make sure that our homepage and how-to guides have a clear entrypoint for this topic, even if we are linking out to Charmcraft for the specifics about how to publish.

Preview of new doc

[dwilding]

FYI @jahn-junior, I want to make sure you've seen this new Ops doc before we publish it. Please let me know if you have any suggestions - thanks!

[tonyandrewmeyer]

Thanks! I think this will definitely help make the site be a more complete picture of charming, and make it easier to figure out how to publish without having to search in a lot of places.

A few suggestions, but happy to approve in advance.

[dwilding]

@tromai would you mind reviewing this when you get time? I need one more reviewer and I would especially like to know whether the explanations of tracks and channels are helpful for someone who might be newer to this stuff!

[tromai]

@tromai would you mind reviewing this when you get time? I need one more reviewer and I would especially like to know whether the explanations of tracks and channels are helpful for someone who might be newer to this stuff!

Absolutely, I will have a look into it.

[tromai]

Thanks for the update.
Everything looks great to me. I really like how the publish step is separated from making the charm discoverable.
I have a comment in publish-your-charm-on-charmhub.md, and am happy to approve the PR after it is resolved.