minor: add missing utility

[distro-setup] / filesystem / usr / share / applications / emacsmail.desktop

#!/usr/bin/env xdg-open
# copied from mutt
[Desktop Entry]
Version=1.0
Type=Application
Terminal=false
Name[en]=emacsmail
Exec=/a/bin/emacsmail %u
Name=emacsmail
MimeType=x-scheme-handler/mailto;
NoDisplay=false
Categories=Office;Network;Email;