Update Babel recipe for AVA 4

Co-authored-by: Mark Wubben <mark@novemberborn.net>

docs/recipes/babel.md

@@ -1,19 +1,21 @@
-# Configuring Babel with AVA 3
+# Configuring Babel with AVA
 
 Translations: [Français](https://github.com/avajs/ava-docs/blob/master/fr_FR/docs/recipes/babel.md)
 
-**This is no longer available in AVA 4.**
-
-You can enable Babel support by installing `@ava/babel`, and then in AVA's configuration setting `babel` to `true`:
+You can enable Babel support by installing [`@babel/register`](https://babeljs.io/docs/en/babel-register) and `@babel/core`, and then in AVA's configuration requiring `@babel/register`:
 
 **`package.json`:**
 
 ```json
 {
 	"ava": {
-		"babel": true
+		"require": [
+			"@babel/register"
+		]
 	}
 }
 ```
 
-Find out more in [`@ava/babel`](https://github.com/avajs/babel).
+`@babel/register` is compatible with CommonJS only. It intercepts `require()` calls and compiles files on the fly. This will compile source, helper and test files.
+
+For more information visit the [Babel documentation](https://babeljs.io/docs/en/babel-register).