Versioned deployments for documentation site

[bo0tzz]

Currently, cloudflare pages automatically pulls and deploys the documentation site on every commit to main. This has been an annoyance with needing to hold off on merging documentation PRs until after a release to avoid confusion. This issue lays out a path to resolve this and pick up a few other shiny things along the way.

The plan is to have the following deployments on cloudflare pages (they call each a "branch"). Each of these lives on its own subdomain under immich.pages.dev.

• feat-foo, deployed for every PR that makes changes to docs/*.
• main, deployed for every push to main that makes changes to docs/*.
• vfoo and release, deployed in the release workflow.

We manually set up custom domains in CF pages for immich.app -> release.immich.pages.dev and main.immich.app -> main.immich.pages.dev. All other deployments are accessed directly on the pages.dev hosts.

Tasks

Beta Give feedback

1. Deploy docs site from github actions with https://github.com/cloudflare/pages-action
2. Deploy docs site to main, release, etc on the appropriate events
3. Custom domains configured for release and main branch deployments
4. Push to preview branches on PR
5. Version switcher in documentation site
6. Version switcher automatically includes all existing versions