Add an option to enable tab bar/barbar.nvim

[tonygoldcrest]

I looked through the configuration options and couldn't find an option to enable the tab bar, or in my case, I would like to use it in combination with https://github.com/romgrk/barbar.nvim. I would like to stay in ZenMode as much as possible but have to switch back and forth to see which buffer I'm currently in and to navigate to the buffer that I need.

Please, consider adding an option to support barbar (not sure if that's different from the tab bar).

Thanks for the great plugin though.