chore: Add engines to package.json
chore: Add engines to package.json

This aims to make explicit the versions of node and npm that
development requires. Unfortunately node and npm do not check
the engines value and so this is purely documentation.

alisd23/finput,ScottLogic/finput,oriondean/finput,oriondean/finput,ScottLogic/finput,ScottLogic/finput,alisd23/finput,oriondean/finput