Hardcoded Gateway URL

[kawaii]

Currently, we hardcode the gateway URL like so;

#| Host to which to connect. Can be overridden for testing e.g.
has Str $.ws-host = 'gateway.discord.gg';

According to the documentation this behaviour is wrong. and in actuality we should be calling the Get Gateway or Get Gateway Bot endpoints for this information.

https://discord.com/developers/docs/topics/gateway#connecting-gateway-url-params

https://discord.com/developers/docs/topics/gateway#get-gateway
https://discord.com/developers/docs/topics/gateway#get-gateway-bot

I think it's still useful to be able to override the gateway URL, so we should keep that in mind when refactoring.