Add some content to the cancer.usegalaxy.eu homepage

[shiltemann]

We made this subdomain a while ago, but never put anything in the homepage.

This is a first pass at adding some resources, similar to the single-cell homepage structure. It is far from complete, but I will send it to the community for additions after it's up

ping @hexylena

[github-actions[bot]]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 23.6%, saving 9.24 KB.

Filename	Before	After	Improvement	Visual comparison
assets/media/logo_cancer.png	39.22 KB	29.98 KB	-23.6%	View diff

344 images did not require optimisation.

[bgruening]

Nice!