Updated the user agent string

httplib.h

@@ -5670,7 +5670,7 @@ inline bool ClientImpl::write_request(Stream &strm, Request &req,
   if (!req.has_header("Accept")) { req.headers.emplace("Accept", "*/*"); }
 
   if (!req.has_header("User-Agent")) {
-    req.headers.emplace("User-Agent", "cpp-httplib/0.7");
+    req.headers.emplace("User-Agent", "cpp-httplib/0.9");
   }
 
   if (req.body.empty()) {