feat: update to vite 2.6 and esbuild 0.13

[dominikg]

also includes update to latest vite-plugin-svelte which uses vite-2.6 api

changeset includes adapters because they also use esbuild and we should stick to a single version (and vite and vite-plugin-svelte also use 0.13 now)

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[changeset-bot]

🦋 Changeset detected

Latest commit: 6a49b15

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@sveltejs/adapter-cloudflare-workers	Patch
@sveltejs/adapter-netlify	Patch
@sveltejs/adapter-node	Patch
@sveltejs/adapter-vercel	Patch
@sveltejs/kit	Patch

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