imp: add unmount top link (#1325)

* imp: add the act type and hyperlink

* revert: act docs

Author: ssi02014

docs/react-testing-library/api.mdx

@@ -31,6 +31,7 @@ as these methods:
 - [`renderHook` Result](#renderhook-result)
   - [`result`](#result)
   - [`rerender`](#rerender-1)
+  - [`unmount`](#unmount-1)
 
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