Upgrade to a newest Node.js version before Node.js v10 maintenance get dropped

Duniter is currently using Node.js v10. This version is the last release in maintenance state before being dropped, as planned, on April 30th of 2021. I am not sure how long would Node.js and TS/JS code would still live in Duniter, but updating Node.js version would allow to get security fixes from Node.js side. https://nodejs.org/en/about/releases/