message: js: fix return type of json kv converter
diff: @@ -362,12 +362,10 @@ export const string: DataConverter<string> = new StringConverter();
  * const buffer = conv.encode(person); // ArrayBuffer
  * const person2 = conv.decode(buffer); // Person
  * ```
  - *
  - * @returns Returns a
  */
  -export const json: <T extends JsonCompatible<T>>() => DataConverter<
  - JsonCompatible<T>
  -> = <T extends JsonCompatible<T>>() => new JSONConverter<T>();
  +export const json: <T extends JsonCompatible<T>>() => DataConverter<T> = <
  + T extends JsonCompatible<T>
  +>() => new JSONConverter<T>();
  /**
  * Returns a converter for [TypedArray](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray) objects.
  