Site icon: separate images for different sizes

[AlexTr]

Now one image is used for all sizes, use separate images for different sizes and add image with bigger dimensions (or increase image_src meta image)

<link rel="shortcut icon" type="image/x-icon" href="icon.png" />

<link rel="image_src" sizes="100x100" href="icon.png" />

<link rel="apple-touch-icon" sizes="152x152" href="icon.png" />