refactor!: welp, a lot of stuff

- Use the OS temp folder to cache the player, closes #57.
- Added support for editing channel name, closes #40.
- Added support for editing channel description.
- Added support for retrieving basic channel analytics, closes #54.
- Moved `Innertube#getAccountInfo()` to `Innertube#account`, and renamed it to `getInfo()`.
- `getInfo()` is now able to return email, channel id, etc.
- Improved jsdoc.

lib/core/PlaylistManager.js

@@ -0,0 +1,115 @@
+'use strict';
+
+const Utils = require('../utils/Utils');
+
+/** @namespace */
+class PlaylistManager {
+  #actions;
+  
+  /**
+   * @param {Actions} actions
+   * @constructor
+   */
+  constructor (actions) {
+    this.#actions = actions;
+  }
+  
+  /**
+   * Creates a playlist.
+   * 
+   * @param {string} title
+   * @param {Array.<string>} video_ids
+   * 
+   * @returns {Promise.<{ success: boolean; status_code: number; playlist_id: string; data: object; }>}
+   */
+  async create(title, video_ids) {
+    Utils.throwIfMissing({ title, video_ids });
+  
+    const response = await this.#actions.playlist('playlist/create', { title, ids: video_ids });
+  
+    return {
+      success: response.success,
+      status_code: response.status_code,
+      playlist_id: response.data.playlistId,
+      data: response.data
+    }
+  }
+  
+  /**
+   * Deletes a given playlist.
+   * @param {string} playlist_id
+   * @returns {Promise.<{ success: boolean; status_code: number; playlist_id: string; data: object; }>}
+   */
+  async delete(playlist_id) {
+    Utils.throwIfMissing({ playlist_id });
+ 
+    const response = await this.#actions.playlist('playlist/delete', { playlist_id });
+    
+    return {
+      success: response.success,
+      status_code: response.status_code,
+      playlist_id,
+      data: response.data
+    }
+  }
+  
+  /**
+   * Adds videos to a given playlist.
+   * 
+   * @param {string} playlist_id
+   * @param {Array.<string>} video_ids
+   * 
+   * @returns {Promise.<{ success: boolean; status_code: number; playlist_id: string; data: object; }>}
+   */
+  async addVideos(playlist_id, video_ids) {
+    Utils.throwIfMissing({ playlist_id, video_ids });
+     
+    const response = await this.#actions.playlist('browse/edit_playlist', {
+      ids: video_ids,
+      action: 'ACTION_ADD_VIDEO',
+      playlist_id
+    });
+
+    return {
+      success: response.success,
+      status_code: response.status_code,
+      playlist_id,
+      data: response.data
+    }
+  }
+  
+  /**
+   * Removes videos from a given playlist.
+   * 
+   * @param {string} playlist_id
+   * @param {Array.<string>} video_ids
+   * 
+   * @returns {Promise.<{ success: boolean; status_code: number; playlist_id: string; data: object; }>}
+   */
+  async removeVideos(playlist_id, video_ids) {
+    Utils.throwIfMissing({ playlist_id, video_ids });
+  
+    const plinfo = await this.#actions.browse(`VL${playlist_id}`);
+
+    const list = Utils.findNode(plinfo.data, 'contents', 'contents', 13, false);
+    if (!list.isEditable) throw new Utils.InnertubeError('This playlist cannot be edited.', playlist_id);
+
+    const videos = list.contents.filter((item) => video_ids.includes(item.playlistVideoRenderer.videoId));
+    const set_video_ids = videos.map((video) => video.playlistVideoRenderer.setVideoId);
+
+    const response = await this.#actions.playlist('browse/edit_playlist', {
+      ids: set_video_ids,
+      action: 'ACTION_REMOVE_VIDEO',
+      playlist_id
+    });
+        
+    return {
+      success: response.success,
+      status_code: response.status_code,
+      playlist_id,
+      data: response.data
+    }
+  }
+}
+
+module.exports = PlaylistManager;