feat: Add the ability to create custom attribute (#2903)

app/javascript/dashboard/api/attributes.js

@@ -0,0 +1,9 @@
+import ApiClient from './ApiClient';
+
+class AttributeAPI extends ApiClient {
+  constructor() {
+    super('custom_attribute_definitions', { accountScoped: true });
+  }
+}
+
+export default new AttributeAPI();