update readme

app/src/Model/MarkdownPage.php

@@ -2,12 +2,22 @@
 
 namespace Lubian\NoFramework\Model;
 
+use Doctrine\DBAL\Types\Types;
+use Doctrine\ORM\Mapping\Column;
+use Doctrine\ORM\Mapping\Entity;
+use Doctrine\ORM\Mapping\GeneratedValue;
+use Doctrine\ORM\Mapping\Id;
+
+#[Entity]
 class MarkdownPage
 {
     public function __construct(
-        public readonly int $id,
-        public readonly string $title,
-        public readonly string $content,
+        #[Id, Column, GeneratedValue]
+        public int|null $id = null,
+        #[Column]
+        public string $title,
+        #[Column(type: Types::TEXT)]
+        public string $content,
     ) {
     }
 }