[Refactor] move new Function helper into a separate file

getAsyncFunc.d.ts

@@ -0,0 +1,5 @@
+import type { AsyncFunction } from '.';
+
+declare function getAsyncFunc(): AsyncFunction | false;
+
+export = getAsyncFunc;

getAsyncFunc.js

@@ -0,0 +1,10 @@
+'use strict';
+
+/** @type {import('./getAsyncFunc')} */
+module.exports = function () {
+	try {
+		return Function('return async function () {}')();
+	} catch (e) {
+		return false;
+	}
+};

index.js

@@ -10,15 +10,7 @@ var isFnRegex = safeRegexTest(/^\s*async(?:\s+function(?:\s+|\()|\s*\()/);
 var hasToStringTag = require('has-tostringtag/shams')();
 var getProto = require('get-proto');
 
-var getAsyncFunc = function () { // eslint-disable-line consistent-return
-	if (!hasToStringTag) {
-		return false;
-	}
-	try {
-		return Function('return async function () {}')();
-	} catch (e) {
-	}
-};
+var getAsyncFunc = require('./getAsyncFunc');
 
 /** @type {import('.').AsyncFunction | false} */
 var AsyncFunction;