refs https://github.com/TryGhost/Toolbox/issues/528
- we're moving towards making Node 18 our recommended version, so that
involves ensuring all of CI is running Node 18
- we still have some Node 16 matrix runs to ensure compatibility
refs https://ghost.slack.com/archives/C02G9E68C/p1685446707169999
- `actions/setup-node` has a bug where it doesn't parse paths where the path is pretty-printed with colors, so we have to explicitly disable colors
- Added whitespace change inside signup-form to trigger new CI run