Add basic mouse support

[Bellavene]

While I am a shortcut's user, sometimes it will be faster to click on a name in the list. Or click a message after scrolling.

[d99kris]

I have been a little hesitant towards adding mouse support, as there are some complexities - for example implementing arbitrary text selection. I'll see if I can find time to do some "feasibility study" on very basic mouse support.

[d99kris]

Unfortunately I think mouse support will be considered out of scope for this project. Will proceed to close this.