[FR] Support ESM out of the box #260

Summary

Our current imports are extension-less, which causes compatibility and ambiguity with ESM mode, deno, debug tooling and module loaders.

Proposal

1. It's cheap and easy to add extensions.
2. After that's done address issues with Feathers in TS + ESM mode as they come

Risks

• The CLI may depend on extensionless imports?

Additional details

I often need/prefer to use modules. This would save me some time. Additionally, having chat support or use ESM by default would strengthen the ecosystem and mark a path towards an ESM only future version.