Add __toString method to Style::class

`__toString` has been added to render `Style::class` to HTML when the instance is treated as string.

src/Style.php

@@ -56,4 +56,14 @@ public function render(): string
             Text::create($ruleset->renderCss())
         );
     }
+
+    /**
+     * Render style to HTML when treated like a string
+     *
+     * @return string
+     */
+    public function __toString()
+    {
+        return $this->render();
+    }
 }