Instance multiplexing & arbitrary instance handling

[SpookySkeletons]

Quite a feat but it would be neat to have the ability to juggle multiple instances simultaneously.

Groups and DMs could be shunted to their respective instance to replace the instance selection feature present in the options menu and allow custom instance domain entry and a visual alert of the associated chat instance host.

Can instance swapping be made more seamless, window-wise?
Resource increase to track more instance hosts simultaneously?
Can CSP be modified on the fly for custom domains?
How hard would it be to strap user hosted FOSScord servers on board like this?

[SpacingBat3]

Well, there was a lot of concepts about FossCord, one was to actually implement a client for it from scratch just so we have a switch between Discord official instances and FossCord as a whole. As of seamless swapping right now we probably want to limit that to conserve the resources (I mean, imagine to have like 4 pages at once while only using the one or two of them). The CSP customization is actually possible (I've implemented a CSPBuilder class for that purpose) to be honest, there's just lack of front-end or anything else to make this available to the user.