Implement directory monitoring using septag/dmon

Use a notification based directory monitoring based on the
septag/dmon lirbary instead of periodically rescan the whole
project's tree.

src/main.c

@@ -14,6 +14,8 @@
   #include <mach-o/dyld.h>
 #endif
 
+#include "dirmonitor.h"
+
 
 SDL_Window *window;
 
@@ -107,6 +109,8 @@ int main(int argc, char **argv) {
   SDL_DisplayMode dm;
   SDL_GetCurrentDisplayMode(0, &dm);
 
+  dirmonitor_init();
+
   window = SDL_CreateWindow(
     "", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, dm.w * 0.8, dm.h * 0.8,
     SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI | SDL_WINDOW_HIDDEN);
@@ -189,6 +193,7 @@ init_lua:
 
   lua_close(L);
   ren_free_window_resources();
+  dirmonitor_deinit();
 
   return EXIT_SUCCESS;
 }