Add support for Svelte v4.

[ota-meshi]

We haven't caught any issues with Svelte v4 yet. Please comment if you think there is a problem in combination with the eslint-plugin.

Related to sveltejs/svelte#8480

[benmccann]

peedDependencies will need to include || ^4.0.0 or || ^4.0.0-next.0

[ota-meshi]

Thank you for letting me know. I will try that later.

[AlexanderKolberg]

The valid-compile rule do not seem to support the new customElement option