feat: todo syntax

moonbit-docs/docs/README.md

@@ -2171,6 +2171,18 @@ Pragmas are annotations inside doc comments. They all take the form `/// @word .
   }
   ```
 
+## Special Syntax
+
+### TODO syntax
+
+The `todo` syntax (`...`) is a special construct used to mark sections of code that are not yet implemented or are placeholders for future functionality. For example:
+
+```moonbit
+fn todo_in_func() -> Int {
+  ...
+}
+```
+
 ## MoonBit's build system
 
 The introduction to the build system is available at [MoonBit's Build System Tutorial](https://moonbitlang.github.io/moon/).

moonbit-docs/i18n/zh/docusaurus-plugin-content-docs/current/README.md

@@ -2152,6 +2152,18 @@ fn reverse[T](xs : Array[T]) -> Array[T] {
   }
   ```
 
+## 特殊语法
+
+### TODO 语法
+
+MoonBit 提供了 `TODO` 语法（`...`），用于标记未完成的代码块。例如：
+
+```moonbit
+fn todo_in_func() -> Int {
+  ...
+}
+```
+
 ## MoonBit 的构建系统
 
 构建系统的介绍参见 [MoonBit 的构建系统教程](https://moonbitlang.github.io/moon/zh/)。