Update PHP version requirement and add PHPStan configuration

Author: rkrx

.gitignore

@@ -2,5 +2,5 @@
 !/src
 !/.gitignore
 !/LICENSE
+!/phpstan.neon
 !/README.md
-

composer.json

@@ -3,7 +3,7 @@
 	"type": "library",
 	"license": "MIT",
 	"require": {
-		"php": ">= 5.3"
+		"php": ">= 7.4"
 	},
 	"autoload": {
 		"psr-4": {
@@ -12,5 +12,11 @@
 	},
 	"suggest": {
 		"rkr/php-di-ioc-adapter": "An adapter for PHP-DI"
+	},
+	"require-dev": {
+		"phpstan/phpstan": "^2.1"
+	},
+	"scripts": {
+		"phpstan": "phpstan analyse -c phpstan.neon"
 	}
-}
+}

phpstan.neon

@@ -0,0 +1,4 @@
+parameters:
+    level: max
+    paths:
+        - src