Think about better integration of intellisense with different Svelte versions

[dummdidumm]

Right now tooling and Svelte(Kit) versions are somewhat disconnected. If you install a version of Svelte that has a new feature, you also need to update your IDE/svelte-check distinctly. The other way around is also a problem: you could be using a new feature where the IDE says it's ok but the Svelte version you have installed can't deal with it. It would be great if we could somehow integrate these things tighter so they don't get out of sync.

Doing this probably means shipping some of the language tool stuff along Svelte. I believe Angular does something similar with their language service. It's not ideal though because people would probably get it unnecessarily if they use an IDE that can't make use of this stuff. It also may make the setup between Svelte and tooling more complicated.

Maybe there's a third way I'm missing right now. Thoughts welcome.