lib: make DOMException attributes configurable and enumerable

The `name`, `message` and `code` attributes of the DOMException
interface should be enumerable and configurable. Aligning
the definition with the Web allows us to use it when
running the Web Platform Tests.

Refs: https://heycam.github.io/webidl/#idl-DOMException

lib/internal/domexception.js

@@ -43,6 +43,12 @@ class DOMException extends Error {
   }
 }
 
+Object.defineProperties(DOMException.prototype, {
+  name: { enumerable: true, configurable: true },
+  message: { enumerable: true, configurable: true },
+  code: { enumerable: true, configurable: true }
+});
+
 for (const [name, codeName, value] of [
   ['IndexSizeError', 'INDEX_SIZE_ERR', 1],
   ['DOMStringSizeError', 'DOMSTRING_SIZE_ERR', 2],