add a emoji and unicode inserter tab

[Michaelzhouisnotwhite]

may be add a feature to let user conveniently pick emoji or other unicode characters like windows clipboard.

I can create a pull request to implement this feature

[hluk]

I would prefer not to have this functionality in the app itself.

Preferably, if there is a command that handles this or just use an external application.

[Michaelzhouisnotwhite]

just like windows. it has a emoji selection area.