Ysul is configured (see D1391) to serve /var/51-wwwroot/rain
as https//rain51.nasqueron.org.
To serve there the development version, the dist/ folder must
be a symlink to this rain51 folder.
But currently, npm start deletes the symlink to recreate a 'dist' folder.
If gump deletes only the content of the dist, symlink is kept and
development version is still served.