make www-data user run npm run build

[alifeee]

currently, the edit script which fires on form submission just replaces the json file in _site with the new one. It should really run npm run build, so things like the RSS feed can be built.

By default, npm does not exist. My user alifeee has access to it via nvm. But, www-data user does not have a home folder, and does not have nvm installed.

I would either

• create a home folder for www-data, install nvm (like for etherpad
• install a version of nvm globally

Then, use

bash .../.nvm/nvm.sh
nvm use 20

in the script somewhere to activate npm