[Auth] Add changelogs for 10.13.0 (#11606)

Added a changelog entry for Firebase Auth 10.13.0.

Author: andrewheard

FirebaseAuth/CHANGELOG.md

@@ -1,3 +1,6 @@
+# 10.13.0
+- [added] Added reCAPTCHA verification support in email authentication flows. (#11231)
+
 # 10.12.0
 - [added] Added support to Firebase Auth to enroll and sign in a user with
   TOTP second factor. (#11261)