Add variable to install YAML extension

Author: vlauciani

docker-compose.yml

@@ -287,6 +287,7 @@ services:
           - INSTALL_BCMATH=${PHP_FPM_INSTALL_BCMATH}
           - INSTALL_MEMCACHED=${PHP_FPM_INSTALL_MEMCACHED}
           - INSTALL_SOCKETS=${LARAVEL_HORIZON_INSTALL_SOCKETS}
+          - INSTALL_YAML=${LARAVEL_HORIZON_INSTALL_YAML}
           - INSTALL_CASSANDRA=${PHP_FPM_INSTALL_CASSANDRA}
           - INSTALL_PHPREDIS=${LARAVEL_HORIZON_INSTALL_PHPREDIS}
           - INSTALL_MONGO=${LARAVEL_HORIZON_INSTALL_MONGO}