Update recommended node version

[mishaschwartz]

Currently the installation documentation recommends at least node 12. We should probably recommend at least version 14 instead and we may want to recommend the latest version if possible.

Another option is to have an actual system dependencies lock file for these sort of things and an install script for system dependencies so that we can just refer to that in the installation documentation. That way the installation steps are simplified and we don't have to update the wiki to keep up with system dependency changes.