Mod file overlay system

Mods can now replace DVD files with contents of their "overlay" folder

(I'll update the docs later when I do a full pass and make non-code mods
more of a first-class citizen)

Fixes https://github.com/TwilitRealm/dusklight/issues/1306

src/dusk/modding/mod_loader.cpp

@@ -14,6 +14,7 @@
 #include <string>
 #include <unordered_map>
 
+#include "aurora/dvd.h"
 #include "dusk/io.hpp"
 #include "miniz.h"
 #include "nlohmann/json.hpp"
@@ -557,6 +558,8 @@ void ModLoader::init() {
         return;
     }
 
+    initOverlayFiles();
+
     DuskLog.info("ModLoader: initializing {} mod(s)...", m_mods.size());
     for (auto& mod : m_mods) {
         buildAPI(mod);