Add better error message for pi.Load

Add information what file is wrong: sprite-sheet.png or custom-font.png

Author: elgopher

print.go

@@ -203,5 +203,9 @@ func loadCustomFont(resources fs.ReadFileFS) error {
 	}
 
 	customFont.Data, err = font.Load(fileContents)
-	return err
+	if err != nil {
+		return fmt.Errorf("invalid custom-font.png: %w", err)
+	}
+
+	return nil
 }

sprite_sheet.go

@@ -29,7 +29,11 @@ func loadSpriteSheet(resources fs.ReadFileFS) error {
 		return fmt.Errorf("error loading sprite-sheet.png file: %w", err)
 	}
 
-	return useSpriteSheet(fileContents)
+	if err = useSpriteSheet(fileContents); err != nil {
+		return fmt.Errorf("invalid sprite-sheet.png: %w", err)
+	}
+
+	return nil
 }
 
 func useSpriteSheet(b []byte) error {