Ability to set custom browser for external Twitch functions

[Coldblackice]

For Chatterino chat/moderation functions that require an external browser (e.g. /user), it'd be great having the ability to define a custom browser to use, similar to setting other external tools (e.g. Streamlink, stream player), instead of having to use the system default browser.

Use case is when the system default browser is "heavy" with addons and/or tabs, and would prefer to have Chatterino open a slimmed, lightweight browser.

[pajlada]

I would be OK with this feature. I would also be ok with this feature being implemented one OS at a time, since I think this would contain a lot of platform-specific code.
I suspect we'd want to optionally specify a custom handler via https://doc.qt.io/qt-6/qdesktopservices.html#url-handlers if the user has specified a custom browser.