feat(Worker): Supporting callback functions like setTimeout, setInterval

Closes #29

app/__tests__/worker_spec.js

@@ -56,6 +56,15 @@ describe("Workers", () => {
       expect(decoded).toBe("test");
     });
 
+    test("It has support for delayed promises with setTimeout", async () => {
+      const worker = new Worker(
+        "foo.com",
+        `addEventListener('test', () => new Promise(resolve => setTimeout(() => resolve(42), 100)))`
+      );
+      const result = await worker.triggerEvent("test");
+      expect(result).toBe(42);
+    })
+
     test("It has support for crypto and Text encoding APIs", async () => {
       const worker = new Worker(
         "foo.com",

app/worker.js

@@ -67,17 +67,33 @@ class Worker {
 
   evaluateWorkerContents(workerContents, kvStores) {
     const context = {
+      // From fetch
       Request,
       Response,
       Headers,
+
+      // URL Standards
       URL,
       URLSearchParams,
+
+      // bas64
       atob,
       btoa,
+
+      // Crypto
       crypto,
       TextDecoder,
       TextEncoder,
-      console
+
+      // Debugging
+      console,
+
+      // Async
+      setTimeout,
+      setInterval,
+      clearTimeout,
+      clearInterval,
+
     };
     const script = new Script(workerContents);
     script.runInContext(