feat: Add Svelte SDK docs

[Lms24]

This PR adds official documentation to the new @sentry/svelte JS SDK which is currently in aplha. It includes

• A disclaimer that this SDK is in alpha and subject to breaking changes
• Instructions for installing and using the SDK in Svelte projects
• Instruction for generating and uploading Sourcemaps in Svelte projects

ref: getsentry/sentry-javascript#5573

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Name	Status	Preview	Updated
sentry-docs	✅ Ready (Inspect)	Visit Preview	Aug 17, 2022 at 10:03AM (UTC)

[lforst]

(Don't know where else to put this.) Do we already have plans to upload a logo for svelte in the docs?

[Lms24]

Haven't done it yet but we either do it when we first publish the docs or when we go into beta. Still need to take a look at how we did it with Remix.

[imatwawana]

This is mostly ready to go, but I've made some styling edits and a few other suggestions. I'd like to give this another review before you merge. Please tag me when it's ready for me to look at again.

[imatwawana]

This section already has a lead-in sentence for the code snippet in the common content (see screenshot below):

So the lead-in text you've added doesn't make sense in this context. I can't make the suggestion directly here because the back ticks from the code snippet interfere, but I'd suggest that you remove the sentence about the button before the code snippet and add the following after the code snippet:

This snippet adds a button that throws an error to a Svelte component.

[Lms24]

Makes sense. I think we have the same problem in the Remix SDK docs (which I took as an example). Will open another PR to adjust this (among some other things I came across)

[Lms24]

Thanks for the great review @imatwawana

Please tag me when it's ready for me to look at again

Updated the PR with all your suggestions. I think this is ready for another round!

[imatwawana]

I made one small comment, but otherwise, this looks great!