Add auto import setting to add file extension to relative imports

[mjbvz]

(Splitting out auto import case from #28288)

Feature Request
Add an option that lets users control if a file extension should be added when importing a file within the current project.

Currently auto import adds imports without a file extension:

import { abc } from './foo'

console.log(abc);

With the new option, we'd instead add the import as:

import { abc } from './foo.js'

console.log(abc);

Related Issues:

• Feature: disable extensionless imports #28288

/cc @RyanCavanaugh

[mjbvz]

Actually I totally already opened this issue two years ago: #24779