Makes onFixedUpdate attach to fixedUpdate (#375)

examples/fixedUpdate.js

@@ -0,0 +1,17 @@
+kaplay();
+
+let fixedCount = 0;
+let count = 0;
+
+onFixedUpdate(() => {
+    fixedCount++;
+});
+
+onUpdate(() => {
+    count++;
+    debug.log(
+        `${fixedDt()} ${Math.floor(fixedCount / time())} ${dt()} ${
+            Math.floor(count / time())
+        }`,
+    );
+});

src/game/events/events.ts

@@ -28,7 +28,7 @@ export function on<Ev extends GameObjEventNames | string & {}>(
 
 export const onFixedUpdate = overload2(
     (action: () => void): KEventController => {
-        const obj = game.root.add([{ update: action }]);
+        const obj = game.root.add([{ fixedUpdate: action }]);
         return {
             get paused() {
                 return obj.paused;