add on_hud_render event

src/logic/scripting/scripting_hud.cpp

@@ -28,6 +28,15 @@ void scripting::on_frontend_init(Hud* hud) {
     }
 }
 
+void scripting::on_frontend_render() {
+    for (auto& pack : engine->getContentPacks()) {
+        lua::emit_event(lua::get_main_thread(), pack.id + ".hudrender", 
+        [&] (lua::State* L) {
+            return 0;            
+        });
+    }
+}
+
 void scripting::on_frontend_close() {
     for (auto& pack : engine->getContentPacks()) {
         lua::emit_event(lua::get_main_thread(), pack.id + ".hudclose", 
@@ -47,5 +56,6 @@ void scripting::load_hud_script(const scriptenv& senv, const std::string& packid
 
     register_event(env, "init", packid+".init");
     register_event(env, "on_hud_open", packid+".hudopen");
+    register_event(env, "on_hud_render", packid+".hudrender");
     register_event(env, "on_hud_close", packid+".hudclose");
 }