add ssr for group bindings

[jonniek]

This PR implements server-rendering for group bindings. I noticed this TODO comment and attempted to add the feature.

svelte/src/compiler/compile/render_ssr/handlers/Element.ts

Line 116 in aa3dcc0

// TODO server-render group bindings

This commit covers the following cases

• group value is a string: checked if value strict equals group value
• group value is an array: checked if value is included in group value array

I didn't see any other data structures for group bindings in docs so I hope this covers everything.

[stale]

This pull request 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.

[Conduitry]

This has been released in 3.39.0 - thank you for your patience!