feat: add hex overlays to web ui

[cthulhustig]

Add support for a new 'hex' overlay type.

Testing:

• Verified hex overlays fill display hex correctly
• Regression tested that rect and circle overlays still displayed correctly when created with url queries

[cthulhustig]

This is something I was hoping to add for Auto-Jimmy. I've not added code for hooking it up to a url query as I'm calling the js directly, I'm happy to add query support if you'd like.

[inexorabletash]

I'll merge this as-is. Thanks!

[cthulhustig]

Thanks mate