feat: add inline jpg and png images to epub

lib/PngToBmpConverter/PngToBmpConverter.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <Print.h>
+#include <SdFat.h>
+
+class PngToBmpConverter {
+ public:
+  // Convert PNG file to 2-bit BMP stream
+  // Similar API to JpegToBmpConverter for consistency
+  static bool pngFileToBmpStream(FsFile& pngFile, Print& bmpOut);
+};