Fix doc (#1024)

Author: qdequippe

README.md

@@ -62,7 +62,7 @@ $ composer require geocoder-php/google-maps-provider php-http/guzzle6-adapter
 Or using the curl client (you'll need to provide a PSR7 implementation such as `nyholm/psr7` if not using guzzle)
 
 ```
-$ composer geocoder-php/google-maps-provider php-http/curl-client nyholm/psr7
+$ composer require geocoder-php/google-maps-provider php-http/curl-client nyholm/psr7
 ```
 
 ### Framework integration