Ensure XDG_RUNTIME_DIR is available to neko

overlay/etc/supervisor.d/neko.ini

@@ -5,7 +5,7 @@ autorestart=true
 priority=30
 user=%(ENV_USER)s
 command=/usr/bin/neko serve --static "/var/www" --display %(ENV_DISPLAY)s --bind :%(ENV_PORT_NOVNC_WEB)s
-environment=HOME="/home/%(ENV_USER)s",USER="%(ENV_USER)s",DISPLAY="%(ENV_DISPLAY)s"
+environment=HOME="/home/%(ENV_USER)s",USER="%(ENV_USER)s",DISPLAY="%(ENV_DISPLAY)s",XDG_RUNTIME_DIR="%(ENV_XDG_RUNTIME_DIR)s"
 stopsignal=INT
 stopwaitsecs=5
 stdout_logfile=/home/%(ENV_USER)s/.cache/log/neko.log