Added PHP 7.4

Author: grimzy

Makefile

@@ -5,7 +5,7 @@ DOCKER_REPO=jestefane/php-dev
 DOCKER_TAG=
 
 # Possible PHP versions: 5.5, 5.6, 7.0, 7.1, 7.2, 7.3
-PHP_VERSIONS=5.5 5.6 7.0 7.1 7.2 7.3
+PHP_VERSIONS=5.5 5.6 7.0 7.1 7.2 7.3 7.4
 
 # Possible PHP variants: cli, fpm
 PHP_VARIANTS=cli fpm