feat(sophora-components): Alternative build setup / clientside-only rendering

[sjockers]

Use plain Svelte and Vite for rendering generic components in Sophora (Datawrapper switcher, highlight cards) without SvelteKit. Rendering is client-side only – which is fine, because there is no meaningful server-side rendering anyways.

Production demo

Pro:

• Direct control of how embeds are rendered on the page (also fixes a long-standing issue that prevents rendering multiple embeds on the same page)
• Fast builds, small bundles
• No problem with mounting code running multiple times: Mounting code for components is just run once per instance, even when multiple instances of an embed are included. This is due to <script type="module"> only being loaded and evaluated once per document, even when referenced multiple times.

Con:

• Some HTML boilerplate needed (could be reduced by creating a template file)
• Minor shimming needed because @swr-data-lab/components builds upon some SvelteKit-only environment variables

Closes #330

[sjockers]

Demo: https://static.datenhub.net/apps/sophora-components/feat/sophora-components-clientside-only/index.html

[awesomephant]

lgtm following offline discussion and pending changes below