fix(core): update

ts/smartstring.base64.ts

@@ -66,4 +66,14 @@ export let base64 = {
   decode: (stringArg: string) => {
     return plugins.jsBase64.decode(stringArg);
   },
+
+  /**
+   *
+   * @param stringArg
+   * checks wether the string is base64 encoded
+   */
+  isBase64: (stringArg: string) => {
+    const regex = /^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)?$/;
+    return regex.test(stringArg);
+  },
 };