Add USA and World grid cartograms from "no days off"

The site https://nodaysoff.run/ by @friggeri contains two grid cartograms for USA and the world. We could add them to the collection.

<img width="335" height="325" alt="Image" src="https://github.com/user-attachments/assets/4f0a64cf-6804-4384-b2d8-19cb3aec904b" />
<img width="877" height="780" alt="Image" src="https://github.com/user-attachments/assets/37682d98-0cab-441f-8e86-86dd3e352829" />