Bad scheme links in readme

[loiccoyle]

Most of the links to the base24 color schemes don't seem the be working. I guess the base24 org got absorbed into tinted-theming so the links go nowhere. Maybe they should be updated to point to the files in the schemes repo or a preview of some sort.

Food for thought:
Maybe you could consider an action to update the lists of base24/16 schemes and have them all point to the schemes repo or a preview page? Because currently to add a new scheme, a PR should be made on the schemes repo, and one on the base24 repo to update the list (which hasn't be done for a lot of the base24 schemes).