Add PNG support for clipboard operations

- Implemented conditional compilation for image copy and retrieval functions in clipboard.cc, clipboard.h, and clipboard.mm, enabling PNG support when YAZE_LIB_PNG is defined.
- Updated graphics_editor.cc and overworld_editor.cc to handle PNG data copying to the clipboard, including error handling for cases when PNG support is disabled.
- Enhanced user feedback by providing alternative actions when PNG export is unavailable, improving overall user experience.

src/app/core/platform/clipboard.cc

@@ -6,9 +6,11 @@
 namespace yaze {
 namespace core {
 
+#if YAZE_LIB_PNG == 1
 void CopyImageToClipboard(const std::vector<uint8_t>& data) {}
 void GetImageFromClipboard(std::vector<uint8_t>& data, int& width,
                            int& height) {}
+#endif
 
 }  // namespace core
 }  // namespace yaze

src/app/core/platform/clipboard.h

@@ -7,8 +7,10 @@
 namespace yaze {
 namespace core {
 
+#if YAZE_LIB_PNG == 1
 void CopyImageToClipboard(const std::vector<uint8_t> &data);
 void GetImageFromClipboard(std::vector<uint8_t> &data, int &width, int &height);
+#endif
 
 }  // namespace core
 }  // namespace yaze

src/app/core/platform/clipboard.mm

@@ -6,6 +6,7 @@
 #ifdef TARGET_OS_MAC
 #import <Cocoa/Cocoa.h>
 
+#if YAZE_LIB_PNG == 1
 void yaze::core::CopyImageToClipboard(const std::vector<uint8_t>& pngData) {
   NSData* data = [NSData dataWithBytes:pngData.data() length:pngData.size()];
   NSImage* image = [[NSImage alloc] initWithData:data];
@@ -41,5 +42,6 @@ void yaze::core::GetImageFromClipboard(std::vector<uint8_t>& pixel_data, int& wi
   CGContextDrawImage(context, CGRectMake(0, 0, width, height), cgImage);
   CGContextRelease(context);
 }
+#endif  // YAZE_LIB_PNG
 
-#endif
+#endif  // TARGET_OS_MAC