Document pointing to a non-default location configuration file (#49)

README.md

@@ -14,7 +14,7 @@ composer require --dev lendable/composer-license-checker
 
 ## Usage
 
-Create a configuration file in your project root, `.allowed-licenses.php`.
+Create a configuration file in your project root, `.allowed-licenses.php` (or you can use the the option `-a / --allow-file` to specify the location of the configuration).
 
 ```php
 <?php
@@ -38,7 +38,7 @@ return (new LicenseConfigurationBuilder())
 ```
 
 ```sh
-./vendor/bin/composer-license-checker
+./vendor/bin/composer-license-checker [--allow-file path/to/configuration_file.php]
 ```
 
 It is suggested you build this into your CI pipeline to automate checking it.