Add variable to install YAML extension

Author: vlauciani

env-example

@@ -251,6 +251,7 @@ NGINX_SSL_PATH=./nginx/ssl/
 ### LARAVEL_HORIZON ################################################
 
 LARAVEL_HORIZON_INSTALL_SOCKETS=false
+LARAVEL_HORIZON_INSTALL_YAML=false
 LARAVEL_HORIZON_INSTALL_PHPREDIS=true
 LARAVEL_HORIZON_INSTALL_MONGO=false
 LARAVEL_HORIZON_INSTALL_FFMPEG=false