Set engines node and npm versions as fixed

[W01fw00d]

• [ ] Unit tests: npm run utest-cover and check coverage
• [ ] Functional tests: npm run dev-front and npm run ftest-mobile and npm run ftest-desktop
• [ ] Run App: npm run build and npm run dev-start -> check that no errors/warnings appear in browser console
• [ ] Run App with Chrome Devtools Mobile Device Screen
• [ ] Upgrade version
• [ ] Update to last version of chemistry-ui
• [ ] Deploy in Heroku before merging in case of potential breaking changes