feat: add TypeScript type definition generation for csv-loader

- Add emitTypes option (default true) to generate .d.ts files
- Add typesOutputDir option for custom output directory
- Generate interface based on CSV schema definitions
- Export RowType for explicit type imports

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

csv-loader.md

@@ -41,6 +41,8 @@ module.exports = {
             bom: true,        // 处理 BOM (默认 true)
             comment: '#',     // 忽略 # 开头的注释行 (默认 '#')
             trim: true,       // 修剪表头和值的前后空格 (默认 true)
+            // emitTypes: false, // 禁用类型定义生成 (默认 true)
+            // typesOutputDir: 'types', // 类型文件输出目录 (可选)
           },
         },
       },
@@ -49,16 +51,35 @@ module.exports = {
 };
 ```
 
+### Generated TypeScript Types
+
+当 `emitTypes: true` 时，loader 会自动生成 `.d.ts` 类型定义文件：
+
+```typescript
+// data.schema.d.ts
+export interface data_schema {
+  name: string;
+  age: number;
+  active: boolean;
+  scores: number[];
+}
+
+export type RowType = data_schema;
+
+declare const data: data_schema[];
+export default data;
+```
+
 ### Importing in TypeScript
 
 ```typescript
 import data from './data.schema.csv';
 
-// data = [
-//   { name: "Alice", age: 30, active: true, scores: [90, 85, 95] },
-//   { name: "Bob", age: 25, active: false, scores: [75, 80, 70] }
-// ]
-```
+// TypeScript 会自动推断类型:
+// data: { name: string; age: number; active: boolean; scores: number[] }[]
+
+// 如果启用了 emitTypes，也可以显式导入类型:
+// import type { RowType } from './data.schema.csv';
 
 ## Options
 
@@ -70,6 +91,8 @@ import data from './data.schema.csv';
 | `bom` | boolean | `true` | Handle byte order mark |
 | `comment` | string \| `false` | `#` | Comment character (set `false` to disable) |
 | `trim` | boolean | `true` | Trim headers and values |
+| `emitTypes` | boolean | `true` | Generate TypeScript declaration file (.d.ts) |
+| `typesOutputDir` | string | `''` | Output directory for generated type files (relative to output path) |
 
 ## Schema Syntax