add new win32 platform implementation (#1224)

* Buffer resources from swap chain were not being released.
* sysgpu Texture.getWidth() should return width not height.
* d3d12: Fixing issues with d3d12 on sysgpu.
* Initial win32 platform

build.zig

@@ -276,6 +276,7 @@ pub const Platform = enum {
     x11,
     wayland,
     web,
+    win32,
 
     pub fn fromTarget(target: std.Target) Platform {
         if (target.cpu.arch == .wasm32) return .web;