docs: note that we use camelCase name for extendable configurations

I regret not making it kebab-case from the beginning, but it's too late
to change.
Besides, if we want to support both camelCase and kebab-case, the
TypeScript suggestion will be a mess (it's sorted in alphabetical order
so you'll see camelCase and kebab-case results mixed together).

README.md

@@ -63,7 +63,7 @@ export default [
       // You can also manually enable the stylistic rules.
       // "stylistic",
 
-      // Other utility configurations, such as `eslint-recommended`,
+      // Other utility configurations, such as `eslintRecommended`, (note that it's in camelCase)
       // are also extendable here. But we don't recommend using them directly.
     ],