How can I use the polygon as a mask, which will make the area in the circle transparent? I cannot manage it
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 100 100">
<circle cx="50" cy="50" r="50" />
<polygon points="20,30 25,20 80,40 80,60 25,80, 20,70 70,50"/>
</svg>