Add 'Channel' to send message

[MelanX]

This adds a way to send a message in another channel than the own one.

Closes #18

[ImDevinC]

The variable looks to be called user_id which I'm guessing is the target user channel. Can we instead change that to channel_id or something a little easier to understand what it's being used for?

[ImDevinC]

Also, can you git commit --amend to change your commit message to match a specific format. Something like feat(message): Add 'Channel' to send message. This will make it show up in the changelog and bump the version number when we do a release.

[ImDevinC]

This looks great, thanks!