Investigate loading community adders from CDN or with npx

[benmccann]

Loading via npx would mean that we need to pass options via CLI and keep that consistent, but are otherwise free to make changes to our APIs.

Loading from something like esm.sh may allow them to have dependencies. That would let them control what version of our AST utils they utilize. That would also let us make changes to those APIs without breaking community adders. We might be able to use https://www.npmjs.com/package/@reejs/imports to help