Clean up dependencies

[teabroker]

After some review I've found dependencies which could be removed for various reasons. Some of them need clarification.

Move to dev dependencies:

• @types/oauth imported internally.
• @types/ws reexported from parsers, but without any particular purpose. I propose to change the interface of parsers from

interface Parser {
  parse(event: WS.MessageEvent) void
}

to something like that:

interface Parser {
  parse(event: {data: string | Buffer | ArrayBuffer | Buffer[]}) void
}

In anyway now it only uses the first argument to consume data property which in its turn has the type similar to what JSON.parse can consume as an argument. So currently I see no need of having WS.MessageEvent as a type.

Remove:

• @types/core-js isn't imported anywhere.
• @types/form-data is deprecated: https://www.npmjs.com/package/@types/form-data