react-native: Add WebSocket ready state constants (#41637)

As defined in the React Native repo.
https://github.com/facebook/react-native/blob/master/Libraries/WebSocket/WebSocket.js#L59-L67

types/react-native/globals.d.ts

@@ -305,4 +305,8 @@ declare var WebSocket: {
             [optionName: string]: any;
         } | null,
     ): WebSocket;
+  readonly CLOSED: number;
+  readonly CLOSING: number;
+  readonly CONNECTING: number;
+  readonly OPEN: number;
 };