Support for mode indicator via tmux-mode-indicator

[rbpatt2019]

Is there an existing issue outlining your improvement?

• I have searched the existing issues and my improvement has not been raised yet.

What would you like to see added and/or changed?

Two in a row, I know, but I was missing these features :P Support for displaying the current mode via tmux-mode-indicator would be great. Are you open to contributions?

[vdbe]

Pull requests are welcome see custom on how to create a module. Don't forget to set the fg/bg for the plugin with it's style options, I don't know how those colors will react with the separators so maybe only use the fg and match bg with the module.

[rbpatt2019]

@vdbe - thanks for the advice! I'll get started in the next couple of days