Remove PNG and ZLIB support from the project

- Eliminated all references to PNG and ZLIB dependencies in CMake configuration and project files.
- Updated documentation to reflect the removal of PNG support and related functionalities.
- Adjusted build scripts and source files to remove unused code related to PNG handling, ensuring a cleaner codebase.

vcpkg.json

@@ -3,14 +3,6 @@
   "version": "0.3.1",
   "description": "Yet Another Zelda3 Editor",
   "dependencies": [
-    {
-      "name": "zlib",
-      "platform": "!uwp"
-    },
-    {
-      "name": "libpng",
-      "platform": "!uwp"
-    },
     {
       "name": "sdl2",
       "platform": "!uwp",