Skeleton 5 compatibility

[MrVauxs]

Skeleton 5 revamped its theme formatting, making the skeleton-4.css import partially not working. Primarily:

layerchart/packages/layerchart/src/lib/styles/skeleton-4.css

Line 9 in e3fc36a

--color-surface-content: var(--base-font-color);

no longer exists, replaced by --typo-base--color-light and --typo-base--color-dark

[techniq]

Hey @MrVauxs, thanks for the heads up. We'll need to create a skeleton-5.css and update the docs for sure.

We also have standalone examples for each of these and will create one for skeleton 5.

I'm a bit covered up at the moment but hopefully we can get to it soon (cc: @cycle4passion), but we also accept PRs if you have some time.