Fix zstd detection in installed httplibConfig.cmake (#2453)

cmake/httplibConfig.cmake.in

@@ -61,7 +61,7 @@ if(@HTTPLIB_IS_USING_ZSTD@)
 	if(${CMAKE_FIND_PACKAGE_NAME}_FIND_REQUIRED)
 		set(httplib_fd_zstd_required_arg REQUIRED)
 	endif()
-	find_package(zstd QUIET)
+	find_package(zstd 1.5.6 CONFIG QUIET)
 	if(NOT zstd_FOUND)
 		find_package(PkgConfig ${httplib_fd_zstd_quiet_arg} ${httplib_fd_zstd_required_arg})
 		if(PKG_CONFIG_FOUND)