docs: Add twoslash-svelte

[Hugos68]

Closes #649

This PR replaced the twoslash with twoslash-svelte package to allow type hints to be available on svelte codeblocks.

Note:
Currently this PR installs the @hugokorte/twoslash-svelte PR, this is because the original/official twoslash-svelte package won't be published until This PR is merged. The code is simply a copy and published seperately.

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time.
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
svelte-dev	❌ Failed (Inspect)			Jan 13, 2025 8:23am

[vercel]

@Hugos68 is attempting to deploy a commit to the Svelte Team on Vercel.

A member of the Team first needs to authorize it.

[Rich-Harris]

Thank you! It looks like line 689 needs updating...

-} else if (language === 'js' || language === 'ts') {
+} else if (language === 'js' || language === 'ts' || language === 'svelte') {

...along with line 700:

-lang: 'ts',
+lang: language === 'svelte' ? language : 'ts',

Though when I make those changes locally, I start seeing errors like this which I I don't really understand 😆 maybe @dummdidumm can make sense of them:

index.tsx
[2304] 128 - Cannot find name 'svelteHTML'.
[2304] 323 - Cannot find name '__sveltets_2_isomorphic_component'.
[2304] 357 - Cannot find name '__sveltets_2_partial'.
[2304] 378 - Cannot find name '__sveltets_2_with_any_event'.

[Hugos68]

Though when I make those changes locally, I start seeing errors like this

Ahh, these are expected! That means something is working, thanks for checking it out, I'll make your changes and continue working on it. I do have to see the Svelte docs rendered is quite the module. Lots of stuff going on.