Develop (#4)

* Update test libs, add new test and fix some docs

* More fix to documents and formats

* Add singleton invokable string resolver

* Add singleton invokable string resolver document

README.md

@@ -124,9 +124,13 @@ use Peroxide\DependencyInjection\Invokables\Singleton;
 $container = new Container([
     // Dependency parent with dependency child
     Dependency::class       => new Singleton(fn() => new Dependency()),
+
     ParentDependency::class => new Singleton(
         fn($container) => new ParentDependency($container->get(Dependency::class))
-    )
+    ),
+
+    // Singleton passing factory as reference string
+    ConcreteClass::class    => new Singleton(ConcreteClassFactory::class)
 ]);
 ```
 The ```Peroxide\DependencyInjection\Invokables\Singleton``` class serves as a wrapper to indicate to our container that we want this class to not create a new instance every time it is retrieved.

README_PT.md

@@ -123,11 +123,15 @@ use Peroxide\DependencyInjection\Container;
 use Peroxide\DependencyInjection\Invokables\Singleton;
 
 $container = new Container([
-    // Dependência pai com dependência filha
+    // Dependência pai com filha.
     Dependency::class       => new Singleton(fn() => new Dependency()),
+
     ParentDependency::class => new Singleton(
         fn($container) => new ParentDependency($container->get(Dependency::class))
-    )
+    ),
+
+    // Singleton passando string como referencia de classe factory
+    ConcreteClass::class    => new Singleton(ConcreteClassFactory::class)
 ]);
 ```
 A classe ```Peroxide\DependencyInjection\Invokables\Singleton``` atua como um invólucro 

composer.json

@@ -12,7 +12,8 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "^10.3"
+        "phpunit/phpunit": "^10.3",
+        "squizlabs/php_codesniffer": "^3.9"
     },
     "autoload-dev": {
         "psr-4": {