meta: add mailmap entry for Ethan-Arrowood

The next update-authors.js run will add a second entry to AUTHORS for
Ethan-Arrowood because they use a new email address in a commit they
authored very recently. Add the new email address to mailmap and update
AUTHORS.

PR-URL: #39930
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>

.mailmap

@@ -123,6 +123,7 @@ Elliott Cable <me@ell.io>
 Eric Phetteplace <phette23@gmail.com>
 Ernesto Salazar <ernestoalbertosalazar@gmail.com>
 Erwin W. Ramadhan <erwinwahyuramadhan@gmail.com>
+Ethan Arrowood <ethan@arrowood.dev> <ethan.arrowood@gmail.com>
 Eugene Obrezkov <ghaiklor@gmail.com>
 Eugene Ostroukhov <eostroukhov@google.com> <eostroukhov@chromium.org>
 Eugene Ostroukhov <eostroukhov@google.com> <eostroukhov@gmail.com>

AUTHORS

@@ -1237,7 +1237,7 @@ Josh Mays <josh.mays@creditcards.com>
 Matt Crummey <mcrummey@validusa.com>
 michael6 <michaelf614@gmail.com>
 Raja Panidepu <rpanidepu@lmdv-rpani.jomax.paholdings.com>
-Ethan Arrowood <ethan.arrowood@gmail.com>
+Ethan Arrowood <ethan@arrowood.dev>
 Dan Villa <danielavilla02@gmail.com>
 CodeTheInternet <edlerner+github@protonmail.com>
 Eric Gonzalez <ericxgonzalez@gmail.com>