Enhance CMake configuration for PNG support and introduce vcpkg.json

- Updated CMakeLists.txt to conditionally enable PNG support based on the presence of the PNG library, improving compatibility for minimal builds.
- Added vcpkg.json to manage project dependencies, including zlib, libpng, sdl2, and abseil, streamlining package management.
- Modified CI workflow in ci.yml to simplify CMake configuration commands for better readability.
- Enhanced CMake scripts to ensure proper handling of dependencies in both minimal and regular builds, improving build reliability.

vcpkg.json

@@ -0,0 +1,12 @@
+{
+  "name": "yaze",
+  "version": "0.3.0",
+  "description": "Yet Another Zelda3 Editor",
+  "dependencies": [
+    "zlib",
+    "libpng",
+    "sdl2",
+    "abseil"
+  ],
+  "builtin-baseline": "c8696863d371ab7f46e213d8f5ca923c4aef2a00"
+}