Create trouble_v3 extension

[fixerer]

Trouble v3 has other filetype (trouble) and other way to get mode.

NB: Only works for single windows, since last_mode is overwritten.

[shadmansaleh]

There's already a trubble extension you should modify that to add support to this.

you can have

M.filetypes = { 'Trouble' , 'trouble'}

So that extension gets loaded on both filetypes. Then update get_trouble_mode to support both. You don't need to create a new extension with a separate name.