Bump minimum version of node + update superagent

[pcothenet]

What

• Bump minimum version of node.js to 18

• Update superagent to fix vulnerability

• Corresponding generator update: https://github.com/patch-technology/client-code-generation/pull/72

SDK Release Checklist

• Have you added an integration test for the changes?
• Have you built the package locally and made queries against it successfully?
• Did you update the changelog?
• Did you bump the package version?
• If endpoints were removed, did you manually remove the corresponding files? (this should be rare)
• For breaking changes, did you plan for the release of the new SDK versions and deploy the API to production?

[pcothenet]

Note: updating this was causing a bunch of problems due to ES modules

[davidcornu]

We should probably go all the way to 18.20.2 while we're at it (https://nodejs.org/en/about/previous-releases)