Custom headers and query params in connection

[heilmela]

Im evaluating the use of colyseus in a "service mesh"-ish topology where the authn/authz is happening on reverse proxy level. That means websocket upgrade requests + all http requests need a token header or access token in the url query params to pass through the proxy and reach the colyseus upstream. (This is especially useful when scaling horizontally since colyseus replicas do NOT need to deal with authn/authz themselves)

This change would be backwards compatible by allowing optional query parms/headers to be added to every request.

@endel WDYT

i would add mock httpie and add tests if the provided headers are landing on the outgoint http requests, if you consider merging