docs(spellcheck): fix spellcheck issues

Author: mikehardy

.spellcheck.dict.txt

@@ -9,6 +9,7 @@ APIs
 APIs.
 AppAttest
 AppCheck
+AppDelegate.m
 APNs
 AirPods
 async

docs/releases/v6.4.0.md

@@ -61,7 +61,7 @@ date: 2020-04-03
 - `Android`: ensure a default notification color is always present when user does not set one
 - `iOS`: calling `registerDeviceForRemoteMessages`/`registerForRemoteNotifications` was incorrectly causing permissions to be requested before explicitly requesting them via the messaging API
 - `iOS`: registering the device was not being called if it was already registered internally.
-  - Devices should **always** register with `registerDeviceForRemoteMessages`, as per Apple guidelines, irregardless of current registration status.
+  - Devices should **always** register with `registerDeviceForRemoteMessages`, as per Apple guidelines, regardless of current registration status.
   - Make sure you **always** call `registerDeviceForRemoteMessages` during your app initialization on iOS
 - `iOS`: in cases where requesting an FCM with the default `scope` & `authorizedEntity`, the underlying code now uses the recommended `instanceIDWithHandler` vs `tokenWithAuthorizedEntity`.
   - This fixes an issue where FCM would throw a `"The operation couldn’t be completed"` error ([`#2657`](https://github.com/invertase/react-native-firebase/issues/2657))