Fix shell script markdown blocks definition

Author: antonkomarev

CONTRIBUTING.md

@@ -21,15 +21,15 @@ Due to time constraints, we are not always able to respond as quickly as we woul
 
 This project comes with a configuration file for php-cs-fixer (.php_cs) that you can use to (re)format your sourcecode for compliance with this project's coding guidelines:
 
-```sh
+```shell script
 $ vendor/bin/php-cs-fixer fix
 ```
 
 ## PHPUnit tests
 
 The phpunit script can be used to invoke the PHPUnit test runner:
 
-```sh
+```shell script
 $ vendor/bin/phpunit
 ```
 

README.md

@@ -24,29 +24,29 @@ Documentation can be found in [Laravel Paket Guide].
 
 Pull in the package through Composer.
 
-```sh
+```shell script
 $ composer require cybercog/laravel-paket --dev
 ```
 
 Run Artisan `paket:setup` command to publish Paket assets to `public/vendor/paket` directory & create `storage/paket` directory for terminal job logs.
 
-```sh
+```shell script
 $ php artisan paket:setup
 ```
 
 ## Upgrading
 
 When upgrading Paket, you should re-publish assets to `public/vendor/paket` directory with force setup command.
 
-```sh
+```shell script
 $ php artisan paket:setup --force
 ```
 
 ## Quick Start
 
 Run local development server.
 
-```sh
+```shell script
 $ php artisan serve
 ```