Typescript support in interactive tutorial and API docs

[opensas]

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Svelte officially supports TypeScript since july 2020, nevertheless this is not reflected in the interactive tutorial nor in the API docs examples.

Describe the solution you'd like

Whenever there svelte/js code there should be an alternative to also see the corresponding svelte/ts version of it.

A button toggle button could be added, like what you can see now in, for example, lit homepage

It could start with the JavaScript version, to make it really clear that Svelte is not forcing you to use TypeScript in any way, but the toggle button will at the same time convey the idea that TypeScript is a first class citizen in Svelte.

How important is this feature to you?
Sometimes I have to goolge around to see how to do something with TypeScript (mainly how to correctly type it), it would be easier if I could just go to the tutorial / API docs and copy paste from the example. It would also be used as a reference for correctly working with TypeScript.

Additional context
It would be great if the REPL could also support TypeScript. There was an issue for that but I couln't find it.