[refactor] Moved "isString()" to its own TS file

utils/helpers/isString.ts

@@ -0,0 +1,7 @@
+/**
+ * Checks whether the value passed in can be considered a string.
+ * @param value The value to check if it is a string.
+ */
+export function isString(value: any): boolean {
+    return (typeof value === "string" || value instanceof String);
+}