feat: display images for each individual hypercert owner in the treemap

[holkexyz]

Example of current treemap: https://hypercerts.org/app/zuzalu/billboard

Instead of the text images are displayed in the spaces that are allocated to the hypercert owners. This issue includes only the change of the treemap itself. Issue #917 describes where the image comes from.

Alternative: Instead of having an image for each hypercert owner, we could just have a background image to improve the aesthetics

[bitbeckers]

Currently in hyperboard. If you want to reopen, let me know what's missing @holkexyz