add descrption for defaultNS in i18nextprovider.md (#143)

Co-authored-by: Aaron_Zhou <[email protected]>

Author: Clarkkkk

Diff for: latest/i18nextprovider.md

@@ -9,17 +9,18 @@ import { I18nextProvider } from 'react-i18next';
 import i18n from './i18n';
 import App from './App';
 
-<I18nextProvider i18n={i18n}>
+<I18nextProvider i18n={i18n} defaultNS={'translation'}>
   <App />
 </I18nextProvider>
 ```
 
 ## When to use?
 
-You will only need to use the provider if you need to support multiple i18next instances - eg. if you provide a component library ([like this example](https://github.com/i18next/react-i18next/tree/master/example/react-component-lib)) or in scenarios for [SSR (ServerSideRendering)](ssr.md).&#x20;
+You will need to use the provider if you need to support multiple i18next instances - eg. if you provide a component library ([like this example](https://github.com/i18next/react-i18next/tree/master/example/react-component-lib)) or in scenarios for [SSR (ServerSideRendering)](ssr.md). Additionally, you have the ability to manage the default namespace(s) by passing defaultNS.
 
 ## I18nextProvider props
 
-| _**name**_ | **type (**_**default)**_ | _**description**_                                                                         |
-| ---------- | ------------------------ | ----------------------------------------------------------------------------------------- |
-| **i18n**   | object (undefined)       | pass i18next instance the provider will pass it down to translation components by context |
+| _**name**_    | **type (**_**default)**_       | _**description**_                                                                         |
+| ------------- | ------------------------------ | ----------------------------------------------------------------------------------------- |
+| **i18n**      | object (undefined)             | pass i18next instance the provider will pass it down to translation components by context |
+| **defaultNS** | string \| string[] (undefined) | pass defaultNS to manage the default namespace(s)                                         |