Revamp website

[trappitsch]

This PR revamps the website to a Zola based page. Except for the CNAME file, it changes the whole content of the repo.

A preview of this website deployed (with an additional disclaimer header) can be found here. Note that I will take this down after the PR is merged and the new website live.

Changes

• Website now uses zola for building and an adjusted zola bearblog theme.
• Menu contains four entries:
  • Home (landing page): New landing page, which is a condensed, prettified version of the WG readme files. This was put together by @BartMassey, @adamgreig, @eldruin, @sirhcel, and myself during a meeting on 2025-11-16 (Meeting 2025-11-11 wg#881 (comment)).
  • Bookshelf: A 1:1 copy of (index and faq pages of) https://docs.rust-embedded.org (repo). This surely needs more work (will be done in a separate PR).
  • Blog and Showcase: Links the externally hosted blog and showcase pages.
• Provide a deploy action that will build the zola page and deploy it to the gh-pages branch on push to master.

Links to discussions we had about this

Here are some links to discussions we had about this revamp recently:

• Meeting 2025-11-04 wg#880 (comment)
• Meeting 2025-11-25 wg#886 (comment)
• Meeting 2025-12-02 wg#888 (comment)
• Meeting 2025-12-02 wg#888 (comment)

What needs to be done when merged

• Ensure that the github pages settings point to the gh-pages branch (I think they point to master right now, but unsure as I can't see that setting).
• Check that rust-embedded.org points to the right place (I think it should be fine as is, this should be DNS settings and the unchanged CNAME file).
• Change the current bookcase repo index file to redirect to the new bookshelf page (tbd after successful deployment of the new page).

It might be good to check in on Matrix before the merge so that we can coordinate in case the deployment needs adjustments :)