Update Node and dependencies

[sadukie]

The past sharp update from dependabot requires a higher version of Node.

The latest LTS is v 20.10.0.

Let's try to upgrade this to the current LTS.

• [ ] Confirm this can work in the dev container.
• [ ] Confirm this will work with Netlify.

[sadukie]

• Works in a dev container
• Works locally (see README for notes on dependencies)
• Works on Netlify (successful deployment to test environment in #334)