fix(docs): userEvent setup broken link (#996)

Author: moshfeu

docs/user-event/intro.mdx

@@ -36,7 +36,7 @@ to test interaction with your components.
 
 ## Writing tests with `userEvent`
 
-We recommend to use [`userEvent.setup()`](setup) when rendering your component
+We recommend to use [`userEvent.setup()`](setup.mdx) when rendering your component
 and inline that rendering and setup in your test or use a setup function.  
 We discourage rendering or using any `userEvent` functions outside of the test
 itself - e.g. in a `before`/`after` hook - for reasons described in