adds usage

README.md

@@ -2,6 +2,34 @@
 
 This PHP 7.1 library is a [PSR-15](https://www.php-fig.org/psr/psr-15/) middleware dedicated to manage static assets like CSS, JS, or image files.
 
+## Usage
+
+```php
+<?php
+use CodeInc\AssetsMiddleware\AssetsMiddleware;
+
+$assetsMiddleware = new AssetsMiddleware(
+    '/assets/' // <-- specifies the assets base URI path
+); 
+
+// adding web assets directories
+$assetsMiddleware->addAssetsDirectory('/path/to/my/first/web-assets-directory');
+$assetsMiddleware->addAssetsDirectory('/path/to/another/web-assets-directory');
+
+// optionally you can limit the acceptable media types
+$assetsMiddleware->setAllowMediaTypes([
+    'image/*',
+    'text/css',
+    'application/javascript'
+]);
+
+// returns the computed path to the assets directory
+$assetsMiddleware->getAssetUri('/path/to/another/web-assets-directory/an-image.jpg');
+
+// processed a PSR-7 server request as a PSR-15 middleware
+$assetsMiddleware->process($aPsr7ServerRequest, $aPsr15RequestHandler); // <-- returns a PSR-7 response
+```
+
 ## Installation
 
 This library is available through [Packagist](https://packagist.org/packages/codeinc/assets-middleware) and can be installed using [Composer](https://getcomposer.org/):