docs: update

src/managers/SessionManager.js

@@ -11,6 +11,12 @@ class SessionManager extends CachedManager {
   constructor(client, iterable) {
     super(client, Session, iterable);
   }
+  /**
+   * The cache of Sessions
+   * @type {Collection<string, Session>}
+   * @name SessionManager#cache
+   */
+
   /**
    * Fetch all sessions of the client.
    * @returns {Promise<SessionManager>}