make extension a recommended rule

[jimmywarting]

It's currently listed as a style rule...

eslint-plugin-node/lib/rules/file-extension-in-import.js

Lines 39 to 40 in f45c614

	category: "Stylistic Issues",
	recommended: false,

however real esm dose not correctly work without it. sources can't guess what you need. it can't scan the filesystem and automatically figure it out, this is not how the browser, deno and node's own esm system works.