Support stricter type for Deno 1.4

It looks like Deno 1.4 is stricter with typing.

The fix is to change WebSocket to be exported as a type at https://github.com/ryo-ma/deno-websocket/blob/master/deps.ts .

export type {
  WebSocket,
} from "https://deno.land/std@0.65.0/ws/mod.ts";

More specifically, it looks like the issue originates from https://deno.land/posts/v1.4#stricter-type-checks-in-code--unstablecode (--unstable flag).

[bebraw]

Great, looks like that one works well. Thanks for the fix. 👍

[bebraw]

Cool, it looks like the fix is simple. To be future-compatible, all we have to do is to change the export.