Update Node.js to v22

[bprusinowski]

Thanks to https://github.com/visualize-admin/visualization-tool/pull/1953, we are now using Node.js 20 in the application (bumped up from 18).

To not immediately jump a few major versions ahead, we should test and make sure the application works correctly after the update to 20; if this is the case, we should consider bumping the Node.js version again, to the next major version supported until April 2027.

[adintegra]

Thank you @bprusinowski 🙇‍♂️ Agree with this approach. v20 should receive maintenance releases through April 2026 so there's no need to rush imho.