Add a "Apply to all windows / containers" option for firefox

[32bitx64bit]

I find it annoying having to switch the user agent every time because im using containers. Please add this option as it is really annoying that chrome has this option but not firefox.

(This is more of a quality of life thing)

[Sada-Mio]

Need feature to allow on all containers by default

I use temporary containers so each new tab is a new container. Manually applying user agent each time is too much work.