docs: add section about customizing components

Author: satya164

docs/pages/1.getting-started.md

@@ -56,7 +56,7 @@ If you have another provider (such as `Redux`), wrap it outside `PaperProvider`
 ```js
 import * as React from 'react';
 import { Provider as PaperProvider } from 'react-native-paper';
-import { Provider as StoreProvider } from 'redux';
+import { Provider as StoreProvider } from 'react-redux';
 import App from './src/App';
 import store from './store';
 

docs/pages/2.theming.md

@@ -103,6 +103,23 @@ export default withTheme(MyComponent);
 
 Components wrapped with `withTheme` support the theme from the `Provider` as well as from the `theme` prop.
 
+## Customizing all instances of a component
+
+Sometimes you want to style a component in a different way everywhere and don't want to change the properties in the theme so that other components are not affected. For example, say you want to change the font of all your buttons, but don't want to change `theme.fonts.medium` because it affects other components.
+
+We don't have an API to do this, because you can already do it with components:
+
+```js
+import * as React from 'react';
+import { Button } from 'react-native-paper';
+
+export default function RoundButton(props) {
+  return <Button theme={{ fonts: { medium: 'Open Sans' } }} {...props} />;
+}
+```
+
+Now you can use `RoundButton` everywhere instead of using `Button`.
+
 ## Gotchas
 
 The `Provider` exposes the theme to the components via [React's context API](https://reactjs.org/docs/context.html), which means that the component must be in the same tree as the `Provider`. Some React Native components will render a different tree such as a `Modal`, in which case the components inside the `Modal` won't be able to access the theme. The work around is to get the theme using the `withTheme` HOC and pass it down to the components as props, or expose it again with the exported `ThemeProvider` component.

src/components/BottomNavigation.js

@@ -48,7 +48,7 @@ type Props<T> = {
    *
    * Each route object should contain the following properties:
    *
-   * - `key`: a unique key to identify the route
+   * - `key`: a unique key to identify the route (required)
    * - `title`: title of the route to use as the tab label
    * - `icon`: icon to use as the tab icon, can be a string, an image source or a react component
    * - `color`: color to use as background color for shifting bottom navigation
@@ -207,6 +207,8 @@ const INACTIVE_LABEL_SIZE = 12;
  * Bottom navigation provides quick navigation between top-level views of an app with a bottom tab bar.
  * It is primarily designed for use on mobile.
  *
+ * For integration with React Navigation, you can use [react-navigation-tabs](https://github.com/react-navigation/react-navigation-tabs).
+ *
  * <div class="screenshots">
  *   <img class="medium" src="screenshots/bottom-navigation.gif" />
  * </div>