RequestHandler: add Example

Shieldon\Psr15\RequestHandler

add($middleware)

• param MiddlewareInterface middleware * The middleware.
• return void

Example:

$finalHandler = new FinalHandler();

$app = new RequestHandler($finalHandler);
$app->add(new ApiMiddleware());
$app->add(new StringMiddleware());

$response = $app->handle(ServerRequestFactory::fromGlobal());