feat: add async function

lib/values/function.ts

@@ -14,6 +14,7 @@ interface FunctionConstructor extends Function {
     (...args: string[]): (...args: any[]) => any;
     new (...args: string[]): (...args: any[]) => any;
     prototype: Function;
+    async<ArgsT extends any[], RetT>(func: (await: <T>(val: T) => Awaited<T>, args: ArgsT) => RetT): Promise<RetT>;
 }
 
 interface CallableFunction extends Function {
@@ -75,4 +76,10 @@ setProps(Function.prototype, {
     toString() {
         return 'function (...) { ... }';
     },
-});
+});
+setProps(Function, {
+    async(func) {
+        if (typeof func !== 'function') throw new TypeError('Expected func to be function.');
+        return internals.makeAsync(func);
+    }
+})