Big class read-only

1. Why enable read-only

Increase the maximum number of people that can be carried in a room and reduce the cost of subscribing to a long connection. (sdk upgrade to latest support)

Detailed description of read-only mode and interactive mode

2. How to enable read-only

2.1 Enable read-only before joining (recommended)

     @interface WhiteRoomConfig : WhiteObject

     @property (nonatomic, assign) BOOL isWritable;

     @end

2.2 Open (or close) read-only after joining

     @interface WhiteRoom : WhiteDisplayer

     - (void)setWritable:(BOOL)writable completionHandler:(void (^ _Nullable)(BOOL isWritable, NSError * _Nullable error))completionHandler;
     @end