ImageViewer 中的焦点指示器遮挡了图像内容

Thank you for developing and maintaining Pyxel. Regarding the focus indicator in the ImageViewer of the pixel editor, the current focus border often covers a large portion of the image area, which can reduce visibility, especially for small or low-resolution images. After testing several alternatives, I found the following two approaches to be effective: drawing an expanded focus border outside the image area, and drawing only L-shaped markers at the four corners. With the corner-only approach, pixel content remains visible while the focus position is still easy to recognize. Screenshots are attached for comparison. In both alternatives, the focus indicator slightly extends outside the image area, but I would appreciate feedback on the overall direction.