[mini.pick] Builtin default mouse mappings

Contributing guidelines

• I have read CONTRIBUTING.md
• I have read CODE_OF_CONDUCT.md

Module(s)

mini.pick

Description

First of all, I would just like to thank everyone that works on mini. It's awesome!

Now, for the feature request proper. I think having builtin, default mouse mappings for scrolling over, choosing and previewing matches in mini.pick would make the user experience a bit more complete. It just feels a tad awkward, not being able to interact with the picker window by mouse even with set mouse=a.

Taking a look at the code, it seems like allowing multiple mappings for the same action would be required to implement this feature (or at least, it seems to me like this would be the most general, clean way to implement this. But I guess you could also use custom mappings). This definitely complicates the plugin a bit, and using the mouse is not all that common anyways, so I'm not sure if you'll find this to be a worthwhile feature. If, however, you agree with me that this would be a nice addition, I'm willing to put in the work to make it happen.

Start by reading the mini.pick mapping implementation and its existing action configuration. Determine how default mouse mappings could support scrolling, choosing, and previewing matches while preserving current keyboard mappings. Done means those interactions work with set mouse=a and the mapping behavior is covered by the module's existing tests, if present.