Support node.js 18, 20

[raucao]

See commits for details.

fixes #1300, fixes #1308, refs #1270

[raucao]

The next step is fixing the documentation dependency hell, which also requires us to use --force for npm installs currently. I think I'll have a go at converting everything to Markdown, and then trying to get as close as possible to the current docs using VitePress and https://www.typedoc-plugin-markdown.org/plugins/vitepress, so we can ditch the whole Python/Sphinx setup entirely and use the latest versions of typedoc and typescript.

[DougReeder]

These are all good changes to modernize the code.