Update create_desktop_file.sh
Update create_desktop_file.sh

Add "Categories=Network;InstantMessaging;" to ensure that Mattermost is listed under the appropriate submenu of the application starter. Tested with KDE/Plasma 5.45 and KMenu.
mattermost/desktop,yuya-oc/desktop,mattermost/desktop,mattermost/desktop,yuya-oc/desktop,mattermost/desktop,yuya-oc/electron-mattermost,yuya-oc/electron-mattermost,mattermost/desktop,yuya-oc/electron-mattermost,yuya-oc/desktop