add all frontend files

node_modules/es-abstract/2021/DaysInYear.js

@@ -0,0 +1,18 @@
+'use strict';
+
+var modulo = require('./modulo');
+
+// https://262.ecma-international.org/5.1/#sec-15.9.1.3
+
+module.exports = function DaysInYear(y) {
+	if (modulo(y, 4) !== 0) {
+		return 365;
+	}
+	if (modulo(y, 100) !== 0) {
+		return 366;
+	}
+	if (modulo(y, 400) !== 0) {
+		return 365;
+	}
+	return 366;
+};