Class directive for components

[AhmadMayo]

Is your feature request related to a problem? Please describe.
Svelte components have the look and feel of vanilla html. Feature requests like #3852 - I'm assuming - supports the argument that svelte developers wants to keep components' props as close to html attributes as possible. Having class directives working with components in the same way they work with html elements would be a nice feature to have for component libraries' developers.

Describe the solution you'd like

<MyComponent class:first class="second" class={condition ? classVar : ''} />

and may be access the compiled prop through $$class // "first second valueOfClassVar" - may be even exclude it from $$restProp?

Describe alternatives you've considered
passing the calculated string to a custom prop (className for example), and let the user handle the logic to calculate the end result of the string.

How important is this feature to you?
Not very important, but I think it would be nice to have it.

Additional context
None

[Conduitry]

See also #4749.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been closed as it was previously marked as stale and saw no subsequent activity.