fix: hardcode 'firefox' as container prefix for waterfox and librewolf

[akdev1l]

Problem

Temporary Containers Automatic mode is not working on firefox forks which customize the value returned as the browser name.

The mismatch means the extension crashes when a new tab opens, an error prints out at the console and the container for the new tab is not created.

Solution

Check if the browser is WaterFox or LibreWolf and then hardcode firefox-default as the container prefix.

I think ideally we would query the browser for the default prefix name (but not sure how to do that as of now)

LibreWolf issue: https://codeberg.org/librewolf/issues/issues/2669 Temporary Containers Issue: https://github.com/stoically/temporary-containers/issues/335