Feature Idea: Add app mode

[Tabiskabis]

I'm using bt almost exclusively to open some URLs in App mode.
For Chrome, the cmd I use is chrome_proxy.exe --app="%url%".
For Firefox it's firefox.exe -taskbar-tab 0 -new-window "%url%" where taskbar-tab is supposed to be a UUID known to Fx, or apparently if it's invalid, is treated as a new "App". The feature is so recent (general availabilty since version 146 iirc) that Mozilla's documentation does not yet mention it.

[aloneguid]

For Chromium-based browsers this already exists, you need to tick "Open in Chromeless window"

Looking into Firefox, didn't know this was supported.