Allow using symfony/yaml 7.*

Author: Patrik Foldes

composer.json

@@ -20,7 +20,7 @@
 	"require": {
 		"php": ">=7.1.0",
 		"ext-json": "*",
-		"symfony/yaml": "^3.4 || ^4 || ^5 || ^6",
+		"symfony/yaml": "^3.4 || ^4 || ^5 || ^6 || ^7",
 		"justinrainbow/json-schema": "^5.2"
 	},
 	"require-dev": {