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/notification/GetUnseenCountEndpoint.ts

@@ -0,0 +1 @@
+export const PATH = '/notification/get_unseen_count';

src/core/endpoints/notification/ModifyChannelPreferenceEndpoint.ts

@@ -0,0 +1,17 @@
+import type { IModifyChannelPreferenceRequest, ModifyChannelPreferenceEndpointOptions } from '../../../types/index.js';
+
+export const PATH = '/notification/modify_channel_preference';
+
+/**
+ * Builds a `/notification/modify_channel_preference` request payload.
+ * @param options - The options to use.
+ * @returns The payload.
+ */
+export function build(options: ModifyChannelPreferenceEndpointOptions): IModifyChannelPreferenceRequest {
+  return {
+    params: options.params,
+    ...{
+      client: options.client
+    }
+  };
+}

src/core/endpoints/notification/index.ts

@@ -0,0 +1,2 @@
+export * as GetUnseenCountEndpoint from './GetUnseenCountEndpoint.js';
+export * as ModifyChannelPreferenceEndpoint from './ModifyChannelPreferenceEndpoint.js';