@slidy/svelte: interactive progress

[EricRovell]

Right now the <Progress /> subcomponent just indicates the overall carousel progress. The idea of @Valexr is to make it interactive, just as <input type="range" />, allow the user to drag the indicator to move through carousel.

There are two options:

• Use the native range input and style it consistently. This way the component is interactive and accessible, but there won't be good style uniformness across the browsers and no sliding transition;
• Implement the interactivity on top of the current component.