changed reference doc

Author: AngelAngelXie

docs-devsite/auth.auth.md

@@ -37,6 +37,7 @@ export interface Auth
 
 |  Method | Description |
 |  --- | --- |
+|  [authStateReady()](./auth.auth.md#authauthstateready) | return a promise that resolves immediately when the initial auth state is settled. The current user might be a valid user, or null if there is no user signed in currently. |
 |  [beforeAuthStateChanged(callback, onAbort)](./auth.auth.md#authbeforeauthstatechanged) | Adds a blocking callback that runs before an auth state change sets a new user. |
 |  [onAuthStateChanged(nextOrObserver, error, completed)](./auth.auth.md#authonauthstatechanged) | Adds an observer for changes to the user's sign-in state. |
 |  [onIdTokenChanged(nextOrObserver, error, completed)](./auth.auth.md#authonidtokenchanged) | Adds an observer for changes to the signed-in user's ID token. |
@@ -144,6 +145,19 @@ const result = await signInWithEmailAndPassword(auth, email, password);
 
 ```
 
+## Auth.authStateReady()
+
+return a promise that resolves immediately when the initial auth state is settled. The current user might be a valid user, or null if there is no user signed in currently.
+
+<b>Signature:</b>
+
+```typescript
+authStateReady(): Promise<void>;
+```
+<b>Returns:</b>
+
+Promise&lt;void&gt;
+
 ## Auth.beforeAuthStateChanged()
 
 Adds a blocking callback that runs before an auth state change sets a new user.