docs: add docs about custom Fonts (#1151)

docs/pages/4.fonts.md

@@ -0,0 +1,60 @@
+---
+title: Fonts
+---
+
+# Fonts
+
+## Installing custom fonts
+
+The easiest way to install custom fonts to your RN project is do as follow:
+
+  1. Define path to asssets directory with fonts in project '`package.json`'
+
+  Example:
+
+  ```js
+    ...
+      "rnpm": {
+        "assets": [
+          "fonts"
+        ]
+      },
+    ...
+  ```
+
+  Note: fonts is a folder with .ttf files
+
+  2. Place your fonts files in your assets folder
+  3. Link fonts files using '`react-native link`' command
+  4. Restart your project to refresh changes
+  5. You are able to use fontFamily based on fonts files
+
+## Configuring fonts in ThemeProvider
+
+After you configure the fonts you need to pass them as font object in a custom theme with the `Provider` component. Check the [default theme](https://github.com/callstack/react-native-paper/blob/master/src/styles/DefaultTheme.js) to see what customization options are supported.
+
+Example:
+
+```js
+import * as React from 'react';
+import { DefaultTheme, Provider as PaperProvider } from 'react-native-paper';
+import App from './src/App';
+
+const theme = {
+  ...DefaultTheme,
+  fonts: {
+      regular: 'Roboto',
+      medium: 'Roboto',
+      light: 'Roboto Light',
+      thin: 'Roboto Thin',
+    },
+};
+
+export default function Main() {
+  return (
+    <PaperProvider theme={theme}>
+      <App />
+    </PaperProvider>
+  );
+}
+```