update with tests

src/wait.ts

@@ -0,0 +1,10 @@
+export function wait(milliseconds) {
+    return new Promise((resolve, reject) => {
+        if (typeof(milliseconds) !== 'number') { 
+        throw new Error('milleseconds not a number'); 
+        }
+
+        setTimeout(() => resolve("done!"), milliseconds)
+    });
+}
+