Add support for DMs

[bendoh]

There wasn't support for direct messages.

This adds it!

Tested on Ubuntu 24.04

[bills-appworks]

Thank you very much for this excellent PR.
Since it includes a relatively large set of features, and due to my own circumstances,
it may take me some time to review and respond. I appreciate your patience.

I will consider integrating it in a positive way.
Please note that I may change the sub command name to something other than convo.

[bills-appworks]

I have incorporated your pull request into the feature/dm-support branch.
I will continue working on it toward the upcoming release.
https://github.com/bills-appworks/bsky-sh-cli/tree/feature/dm-support

[bills-appworks]

After reviewing the contents, I found that a few adjustments will be necessary before the release.
Due to my own circumstances, the release may still take some time, and I apologize for the delay.