feat(@vtmn/react, @vtmn/vue): manage height parameter of `VtmnSkeleton` component

[thollander]

Changes description

unit has non-sense to be managed inside this component, we should instead rely on CSS API instead of managing all possible unit values inside our components. If the value is not correct, CSS will manage it its way.

from <VtmnSkeleton width="100" /> to <VtmnSkeleton width="100%" /> or <VtmnSkeleton width="100px" />

Also add a height parameter which follows this same logic too. <VtmnSkeleton width="100%" height="2em" />

Context

Closes https://github.com/Decathlon/vitamin-web/issues/1403

Checklist

• [x] Make sure you are requesting to pull a topic/feature/bugfix branch. Please, don't request directly from your main!
• [x] Check commits & PR names matches our requested structure. It must follow the https://www.conventionalcommits.org pattern.
• [x] Check your code additions will fail neither code linting checks.
• [x] I have reviewed the submitted code.
• [x] I have tested on related showcases.
• [x] If it includes design changes, please ask for a review design-system-core-team-design GitHub team.

Does this introduce a breaking change?

• Yes

Other information

Linked to https://github.com/Decathlon/vitamin-web/pull/1404 (svelte impl)

BREAKING CHANGE: remove unit from VtmnSkeleton, it should now be passed in the width or height directly