refactor: add ready getter that returns a promise hooked on the open event

src/index.ts

@@ -6,6 +6,8 @@ import b4a from "b4a";
 const ID = b4a.from("lumeweb");
 
 export default class RPC extends ProtomuxRPC {
+  private _ready: Promise<void>;
+
   constructor(stream: any, options = {}) {
     options = {
       ...{
@@ -15,9 +17,17 @@ export default class RPC extends ProtomuxRPC {
       ...options,
     };
     super(stream, options);
+    this._ready = new Promise((resolve) => {
+      // @ts-ignore
+      this.on("open", resolve);
+    });
   }
 
   async request(method: any, value: any | string = "", options = {}) {
     return super.request(method, value, options);
   }
+
+  get ready(): Promise<void> {
+    return this._ready;
+  }
 }