TLDR: Migrate to latest SvelteKit

The previous SvelteKit that was used in doc-builder was an pre-1.0 release one. There has been a lot of changes on SvelteKit, including new routing mechanism. Overall, it is a good time to migrate to the latest sveltekit and keep doc-builder up-to-date

Not sure if there will be any performance gains in building doc html files. If so, that would be nice.

todos:

• remove unnecessary dev files
• python copying mdx files should put them in new sveltekit 1.0 [slug]/page.svelte format bfcaa45
• test it intensively locally (tested it on datasets docs)
• check objects.inv file location being correct
• test it on transformers docs (make sure paths in translated pages are working as expected) [wip testing doc-builder] transformers#26027 link to workflow
  • pushed doc file here
  • newly built doc files causing 500 internal server error (fix this error) (fixed b0bbce4)
• title not changing (page should reload on click) (handled in hub pr)
• left side menu not changing (handled in hub pr)
• fix failing test (fixed transformersd dep bf1b146)
• revert dev doc build action changes