Update xmtp-js code annotations to provide more meaningful generated TypeDocs

[jhaaaa]

• As @mkobetic thoughtfully pointed out, the TypeDocs generated from code annotations to xmtp-js aren't as robust as we'd like.
• @neekolas also mentioned that the "Type aliases" and "Variables" sections in the currently generated docs could be made to be more useful and the section titles could be more meaningful: https://xmtp-js.pages.dev/modules.
• From @richbustos - might there be a way to include code samples in the reference docs? Is this something that TypeDoc will enable us to do? If yes, let's do it. If not, we need to find another way to deliver code samples for every method.
• How might @jhaaaa help with the writing process?
• How might we break this work up into phases? What are the most important methods that we should address first?

[jhaaaa]

Closing this as stale for now. We have not received any negative feedback about the ref docs as they are. We'll open a new issue if we hear feedback that indicates we need to improve code annotations.