Enhancement: Set a filetype

[ferdinandrau]

Would it be possible to set the filetype of the window to something unambiguous (like arrow-nvim-prompt for example)? That way one could easily create a custom statusline on that filetype, which would be nice. 🙃

[NickvanDyke]

I would also appreciate that, so I can ignore it in lualine's windows component. Atm it'll show as [No Name] when the prompt is open.