docs: add markdown plugin documentation

Author: NoOne7135

adminforth/documentation/docs/tutorial/05-Plugins/14-markdown.md

@@ -0,0 +1,35 @@
+# Markdown
+
+The Markdown plugin enables Markdown support in AdminForth, allowing users to create and edit records using Markdown syntax.
+
+## Installation
+
+To install the plugin:
+
+```bash
+npm install @adminforth/markdown --save
+```
+
+### Usage
+
+Configure the plugin in your apartments resource file:
+
+```typescript title="./resources/apartments.ts"
+import MarkdownPlugin from '@adminforth/markdown';
+
+// ... existing resource configuration ...
+
+plugins: [
+  new MarkdownPlugin({fieldName: "description"}),
+]
+```
+
+Here is how it looks in create view:
+
+![alt text](markdown.png)
+
+Here is how it looks in show view:
+
+![alt text](markdown-show1.png)
+![alt text](markdown-show2.png)
+