- 更新index.d.ts

- 导出了部分类型，这是为了支持类型测试
  - 为`Document`添加泛型
  - 在`Document`实例化时传入doc的类型，它将为所有返回doc的方法提供正确的类型
  - 自动推断`search`,`searchCache`,`searchAsync`的返回类型，现在他们不再返回联合类型
  - 为上述方法的`limit`参数单独使用函数重载，增加可读性

- 更新types.ts
  测试ts静态类型

test/types.ts

@@ -1,16 +1,33 @@
-import { Document } from 'flexsearch'
-import '../index'
+import { DefaultDocumentSearchResults, Document, Resolver } from "flexsearch";
+import "../index";
 
 const document = new Document<{
-  title: string
-  description: string
-  tags: string[]
-}>({})
+    title: string
+    description: string
+    tags: string[]
+}>({});
 
 async function test() {
-  const doc = await document.searchAsync('test', {
-    enrich: true,
-    pluck: 'test',
-  })
+    // The correct type
+    const doc1 = await document.searchAsync({});
+    const doc2: Resolver = await document.searchAsync({
+        resolve: true,
+    });
+    const doc3 = await document.searchAsync({
+        enrich: true,
+    });
+    const doc4 = await document.searchAsync({
+        enrich: true,
+        merge: true,
+    });
+    doc4[0].doc.title;
+    // The wrong type
+    // @ts-expect-error
+    const docw1: Resolver = await document.searchAsync({});
+    // @ts-expect-error
+    const docw2: DefaultDocumentSearchResults = await document.searchAsync({
+        enrich: true,
+    });
+    // ...
 }