docs: add FAQ page and native features question (#979)

* docs: add FAQ page and native features question

* docs: fixed grammar issues & added native examples

Author: mdjastrzebski

website/docs/FAQ.md

@@ -0,0 +1,33 @@
+---
+id: faq
+title: FAQ
+---
+
+<details>
+  <summary>Can I test native features of React Native apps?</summary>
+
+<br />
+<p>Short answer: no.</p>
+
+React Native Testing Library does not provide a full React Native runtime since that would require running on physical device
+or iOS simulator/Android emulator to provision the underlying OS and platform APIs.
+
+Instead of using React Native renderer, it simulates only the JavaScript part of its runtime by 
+using [React Test Renderer](https://reactjs.org/docs/test-renderer.html) while providing queries
+and `fireEvent` APIs that mimick certain behaviors from the real runtime.
+
+This approach has certain benefits and shortfalls. On the positive side:
+
+- it allows testing most of the logic of regular React Native apps
+- it allows running test on any OS supported by Jest, or other test runner, e.g. on CI
+- it uses much less resources than full runtime simulation
+- you can use Jest fake timers
+
+The the negative side:
+
+- you cannot test native features
+- certain JavaScript features might not be perfectly simulated, but we are working on it
+
+For instance, [react-native's ScrollView](https://reactnative.dev/docs/scrollview) has several props that depend on native calls. While you can trigger `onScroll` call with `fireEvent.scroll`, `onMomentumScrollBegin` is called from the native side and will therefore not be called.
+
+</details>

website/sidebars.js

@@ -7,6 +7,7 @@ module.exports = {
       'migration-v7',
       'migration-v2',
       'how-should-i-query',
+      'faq',
       'eslint-plugin-testing-library',
     ],
     Examples: ['react-navigation', 'redux-integration'],