Add a "going to prod" section to snaps documentation

[ziad-saab]

AC:

• "Publish your snap" (https://docs.metamask.io/snaps/how-to/develop-a-snap/#publish-your-snap) moved to its own document called something like "Going to prod" (TBD)
• "Going to prod" section has instructions on how to move from local:http://localhost.. to npm:packageName in the Dapp

[Montoya]

I like this! We may want to give advice about publishing the dapp too. I've seen some snap developers not fully understand this. I've also seen some that are not experienced with npm and run into confusion around how to update the package.json.