refactor!: overhaul core classes and remove redundant code (#388)

* feat(Player.ts): append `cver` to deciphered URLs

* refactor(Actions.ts): remove redundant `getVideoInfo` function

This is leftover code from previous versions. It had many problems and it is no longer required.

* fix(Kids.ts): remove unneeded `await` keywords

* dev: add more endpoints

* chore: update deps

* refactor: separate endpoints into files

* dev: improve types

* dev: add more endpoints

* refactor: put clients in a separate directory inside `core`

* chore: lint

* refactor: move mixins and managers to separate folders

* chore: fix tests

* dev: add `CreateVideoEndpoint`

* chore: clean up

* chore: lint

* chore: add some comments

* chore: remove unnecessary test

* dev: add `playlist/CreateEndpoint`

* dev: add `playlist/DeleteEndpoint`

* dev: add `browse/EditPlaylistEndpoint`

* fix(parser): add a few checks to avoid parsing errors

src/core/endpoints/NextEndpoint.ts

@@ -0,0 +1,21 @@
+import type { INextRequest, NextEndpointOptions } from '../../types/index.js';
+
+export const PATH = '/next';
+
+/**
+ * Builds a `/next` request payload.
+ * @param opts - The options to use.
+ * @returns The payload.
+ */
+export function build(opts: NextEndpointOptions): INextRequest {
+  return {
+    ...{
+      videoId: opts.video_id,
+      playlistId: opts.playlist_id,
+      params: opts.params,
+      playlistIndex: opts.playlist_index,
+      client: opts.client,
+      continuation: opts.continuation
+    }
+  };
+}