Add StateBearer which can carry state

src/Parsedown.php

@@ -25,9 +25,9 @@ final class Parsedown
     /** @var State */
     private $State;
 
-    public function __construct(State $State = null)
+    public function __construct(StateBearer $StateBearer = null)
     {
-        $this->State = $State ?: new State;
+        $this->State = ($StateBearer ?: new State)->state();
     }
 
     /**

src/State.php

@@ -5,7 +5,7 @@ namespace Erusev\Parsedown;
 use Erusev\Parsedown\AST\StateRenderable;
 use Erusev\Parsedown\Html\Renderable;
 
-final class State
+final class State implements StateBearer
 {
     /**
      * @var array<class-string<Configurable>, Configurable>
@@ -88,4 +88,12 @@ final class State
             $StateRenderables
         );
     }
+
+    /**
+     * @return State
+     */
+    public function state()
+    {
+        return $this;
+    }
 }

src/StateBearer.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Erusev\Parsedown;
+
+interface StateBearer
+{
+    /**
+     * @return State
+     */
+    public function state();
+}