Upgrade Jekyll and replace github-pages meta-gem with github action

[erikrozendaal]

After merging to master the Github site settings need to be reconfigured to use an action-based build instead of the legacy build.

[Copilot]

Pull request overview

Updates the documentation site toolchain to build with a GitHub Actions Pages workflow instead of relying on the github-pages meta-gem, and refreshes the docs’ Ruby/Jekyll dependency set accordingly.

Changes:

• Adds a GitHub Actions workflow to build and deploy docs/ to GitHub Pages.
• Replaces github-pages with a direct Jekyll 4.4.x + plugin Gemfile for the docs site and updates the lockfile.
• Updates local dev dependencies (Nix) to support the new docs gem set (e.g., OpenSSL).

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
flake.nix	Adds OpenSSL to the dev environment to support updated native/build dependencies for docs tooling.
docs/Gemfile	Switches docs to jekyll ~> 4.4 and explicit plugins, removing github-pages.
docs/Gemfile.lock	Refreshes/resolves docs gem dependencies for the new Jekyll/plugin set.
docs/.ruby-version	Aligns docs Ruby version with the updated toolchain.
.github/workflows/pages.yml	Introduces an action-based build + deploy pipeline for GitHub Pages from docs/.

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