Updates the docs structure, navigation etc to be easier + better suited
for showing Nx technology support beyond just TS.
**Notes:**
- API (`/nx-api`) tab is removed from the navigation (i.e. menu bar),
but pages still remain for now until we update references in `*.md`
files.
- Redirects are set up `/nx-api` to go to their respect new location
e.g. `/technologies` or `/reference/core-api`
- Old URLs still exist in the sitemap for now, but majority of them will
be redirected -- a follow-up PR can remove them.
**Preview:**
https://nx-dev-git-nx-dev-polyglot-docs-restructure-nrwl.vercel.app/docs
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Co-authored-by: Jack Hsu <jack.hsu@gmail.com>
