ensure a clear and consistent convention for when to use file extensions

[thescientist13]

Type of Change

• New Feature Request
• Documentation / Website
• Improvement / Suggestion
• Bug
• Other (please clarify below)

Summary

The ESM spec requires file extensions, but almost all developers expect to be able to

import { something } from 'foo';

This is typically true of modules in node_modules, but this will break if you are trying to access a file in your own project. ex.

import { something } from '/components/footer/footer';

Details

The first case works because of the importMap but we should probably establish a singe default way of doing things, or at least clear explanation of when if we need to support both. Or maybe an opportunity for a plugin for extension-less files, like in webpack?