Add missing field to firebase claim in token result

Author: sam-gc

common/api-review/auth.api.md

@@ -828,4 +828,4 @@ export function verifyBeforeUpdateEmail(user: User, newEmail: string, actionCode
 export function verifyPasswordResetCode(auth: Auth, code: string): Promise<string>;
 
 
-```
+```

packages/auth/src/model/public_types.ts

@@ -101,6 +101,7 @@ export interface ParsedToken {
   'firebase'?: {
     'sign_in_provider'?: string;
     'sign_in_second_factor'?: string;
+    'identities'?: Record<string, string>;
   };
   /** Map of any additional custom claims. */
   [key: string]: string | object | undefined;