util: add missing header for libc++

hyprcursor-util/src/main.cpp:260:19: error: implicit instantiation of undefined template 'std::basic_ofstream<char>'
  260 |     std::ofstream manifest(out + "/manifest.hl", std::ios::trunc);
      |                   ^
/usr/include/c++/v1/__fwd/fstream.h:26:28: note: template is declared here
   26 | class _LIBCPP_TEMPLATE_VIS basic_ofstream;
      |                            ^
hyprcursor-util/src/main.cpp:292:41: error: implicit instantiation of undefined template 'std::basic_ifstream<char>'
  292 |         std::ifstream                   xconfig("/tmp/hyprcursor-util/" + xcursor.path().stem().string() + ".conf");
      |                                         ^
/usr/include/c++/v1/__fwd/fstream.h:24:28: note: template is declared here
   24 | class _LIBCPP_TEMPLATE_VIS basic_ifstream;
      |                            ^
hyprcursor-util/src/main.cpp:370:23: error: implicit instantiation of undefined template 'std::basic_ofstream<char>'
  370 |         std::ofstream meta(CURSORDIR + "/meta.hl", std::ios::trunc);
      |                       ^
/usr/include/c++/v1/__fwd/fstream.h:26:28: note: template is declared here
   26 | class _LIBCPP_TEMPLATE_VIS basic_ofstream;
      |                            ^

hyprcursor-util/src/main.cpp

@@ -2,6 +2,7 @@
 #include <zip.h>
 #include <optional>
 #include <filesystem>
+#include <fstream>
 #include <array>
 #include <format>
 #include <algorithm>