Proxy Transports

A universal interface for designing "transports", i.e. ways of sending https+wss traffic from the browser through a proxy.

A transport is an object that implements the ProxyTransport interface.

``js
export interface ProxyTransport {
init: () => Promise;
ready: boolean;
connect: (
url: URL,
protocols: string[],
requestHeaders: RawHeaders,
onopen: (protocol: string, extensions: string) => void,
onmessage: (data: WebSocketDataType) => void,
onclose: (code: number, reason: string) => void,
onerror: (error: string) => void
) => [
(data: WebSocketDataType) => void,
(code: number, reason: string) => void,
];

request: (
remote: URL,
method: string,
body: BodyInit | null,
headers: RawHeaders,
signal: AbortSignal | undefined
) => Promise;
}
``

Successor to bare-mux