bug(@vtmn/svelte): linear progressBar not displayed correctly on storybook

## Description
On the svelte storybook, on every `linear` version of the `VtmnProgressbar` component ([link](https://decathlon.github.io/vitamin-web/@vtmn/showcase-svelte/?path=/story/components-indicators-vtmnprogressbar--overview&args=size:small)), the progress displayed (blue background on the progress element) is always at 100%.

=> This error only affect storybook. The component himself is working properly.

This error occurs because the following CSS code is missing.

```css
transform: var(--vtmn-progressbar_progress-transform);
```

## Expected behavior
As for every other languages, the progress should be reflected on the component as in the exemple bellow.

## Version affected
@vtmn/svelte: v3.2.5