Add speech synthesis support

include/fmt/os.h

@@ -200,6 +200,11 @@ FMT_API void report_windows_error(int error_code,
                                   string_view message) FMT_NOEXCEPT;
 #endif  // _WIN32
 
+template <typename S, typename... Args, typename Char = char_t<S>>
+void say(const S& format_str, Args&&... args) {
+  std::system(format("say \"{}\"", format(format_str, args...)).c_str());
+}
+
 // A buffered file.
 class buffered_file {
  private: