Add combineURLs helper

lib/helpers/combineURLs.js

@@ -0,0 +1,12 @@
+'use strict';
+
+/**
+ * Creates a new URL by combining the specified URLs
+ *
+ * @param {string} baseURL The base URL
+ * @param {string} relativeURL The relative URL
+ * @returns {string} The combined URL
+ */
+module.exports = function combineURLs(baseURL, relativeURL) {
+  return baseURL.replace(/\/+$/, '') + '/' + relativeURL.replace(/^\/+/, '');
+};