Fix build error

index/listing.cpp: In function ‘std::string index_listing(Webserver_Request&, std::string)’:
index/listing.cpp:113:51: error: variable ‘constexpr const std::array<std::basic_string_view<char>, 5> downloadable_suffixes’ has initializer but incomplete type
  113 |         constexpr std::array<std::string_view, 5> downloadable_suffixes {
      |                                                   ^~~~~~~~~~~~~~~~~~~~~

#929

index/listing.cpp

@@ -18,6 +18,8 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 
 #include <forward_list>
+#include <array>
+#include <string_view>
 #include <index/listing.h>
 #include <assets/view.h>
 #include <assets/page.h>