update md

Author: kyun

common/api-review/auth.api.md

@@ -538,6 +538,7 @@ export interface ParsedToken {
     'auth_time'?: string;
     'exp'?: string;
     'firebase'?: {
+        'identities': { [key: string]: string[] };
         'sign_in_provider'?: string;
         'sign_in_second_factor'?: string;
     };