[Docs] Dead Links for Space and Progress

[DaveL17]

Link to the page(s) where something isn't quite right

https://svelteui.dev/core/space, https://svelteui.dev/core/progress

Exact quote of what is wrong

Pages make reference to theme.spacing and theme.radius (which are appropriate) but their related links are to a route that doesn't exist:

https://svelteui.dev/theming/extend-theme/#spacing-radius-and-shadows (throws a 404).

I'm willing to help make repairs, but I'm not sure whether the links should point to a different resource, or if the missing resource needs to be created (I'm under qualified to help with the latter).

Are you willing to create pull request with the fix?

Yes