fix: add export type (#540)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Introduced `ClientOptions` for enhanced configuration of HTTP clients.
- Added `CheckAddressFunction` for improved address validation
capabilities.
  
- **Compatibility**
- Existing exports remain unchanged, ensuring compatibility with
previous versions.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: shixia.ly <[email protected]>

Author: akitaSummer

src/index.ts

@@ -43,14 +43,16 @@ export {
 // HttpClient2 is keep compatible with urllib@2 HttpClient2
 export {
   HttpClient, HttpClient as HttpClient2, HEADER_USER_AGENT as USER_AGENT,
-  RequestDiagnosticsMessage, ResponseDiagnosticsMessage,
+  RequestDiagnosticsMessage, ResponseDiagnosticsMessage, ClientOptions,
 } from './HttpClient.js';
 // RequestOptions2 is keep compatible with urllib@2 RequestOptions2
 export {
   RequestOptions, RequestOptions as RequestOptions2, RequestURL, HttpMethod,
   FixJSONCtlCharsHandler, FixJSONCtlChars,
 } from './Request.js';
 
+export { CheckAddressFunction } from './HttpAgent.js';
+
 export {
   SocketInfo, Timing, RawResponseWithMeta, HttpClientResponse,
 } from './Response.js';