docs: add renderer doc

Author: joshuaellis

docs/renderer.md

@@ -0,0 +1,61 @@
+---
+name: Renderer
+route: '/renderer'
+---
+
+# Render Engine
+
+## Overview
+
+React requires a rendering engine, typically when creating an application people use `react-dom`.
+When running tests, React still requires an engine. We currently support two different engines –
+`react-test-renderer` & `react-dom`. If you have both installed in your project, by default we will
+use `react-test-renderer`, assuming you're using the default imports:
+
+```js
+import { renderHook } from '@testing-library/react-hooks'
+```
+
+It does this because the library runs a check for available renderers, in the order:
+
+- `react-test-renderer`
+- `react-dom`
+
+If neither are available you will see an error asking you to check that one of the above is
+installed. If only one is installed, then it will use that renderer.
+
+## Being specific
+
+If, however, for certain tests you want to use a specific renderer (e.g. you want to use `react-dom`
+for SSR) you can import the server module directly:
+
+```ts
+import { renderHook } from '@testing-library/react-hooks/server`
+```
+
+We have the following exports available:
+
+```ts
+import { renderHook, act } from '@testing-library/react-hooks' // will try to auto-detect
+
+import { renderHook, act } from '@testing-library/react-hooks/dom' // will use react-dom
+
+import { renderHook, act } from '@testing-library/react-hooks/native' // will use react-test-renderer
+
+import { renderHook, act } from '@testing-library/react-hooks/server' // will use react-dom
+```
+
+## Caveats
+
+### SSR
+
+While calling `renderHook` from `@testing-library/react-hooks/native` and
+`@testing-library/react-hooks/dom` will return the same `RenderHookResult` as documented
+[here](/reference/api#renderhook-result), using `@testing-library/react-hooks/server` will return an
+additional function:
+
+```ts
+hydrate: () => void
+```
+
+For more information on `hydrate` see the [API documentation](/reference/api#hydrate)

doczrc.js

@@ -19,6 +19,7 @@ export default {
   menu: [
     { name: 'Introduction' },
     { name: 'Usage', menu: ['Basic Hooks', 'Advanced Hooks'] },
+    { name: 'Renderer' },
     { name: 'API Reference' }
   ]
 }