feat(api): Implement received hand event handling and UI updates

knockoutwhistweb/public/javascripts/websocket.js

@@ -1,7 +1,9 @@
+type EventHandler = (data: any) => any | Promise<any>;
+
 // javascript
 let ws = null; // will be created by connectWebSocket()
-const pending = new Map(); // id -> { resolve, reject, timer }
-const handlers = new Map(); // eventType -> handler(data) -> (value|Promise)
+const pending: Map<string, any> = new Map(); // id -> { resolve, reject, timer }
+const handlers: Map<string, EventHandler> = new Map(); // eventType -> handler(data) -> (value|Promise)
 
 
 let timer = null;
@@ -180,7 +182,7 @@ function sendEventAndWait(eventType, eventData, timeoutMs = 10000) {
     return p;
 }
 
-function onEvent(eventType, handler) {
+function onEvent(eventType: string, handler: EventHandler) {
     handlers.set(eventType, handler);
 }