feat: add authorization header to link checker

[esolitos]

Adds an authorization header to the link checker command using a
GitHub App token. This allows the link checker to access private
repositories and pages that require authentication.

[Copilot]

Pull Request Overview

This PR adds an authorization header to the jekyll link checker job so that it can access private repositories and pages using a GitHub App token.

• Adds a new step using actions/create-github-app-token@v2 to generate a token.
• Passes the token via an environment variable (REQ_TOKEN) into the link checker command.
• Injects the token into the typhoeus configuration within the link checker invocation.

Comments suppressed due to low confidence (2)

.github/workflows/jekyll-link-checker.yml:155

• [nitpick] Consider renaming REQ_TOKEN to a more descriptive name (e.g., LINK_CHECKER_TOKEN) to clarify its purpose for future maintainers.

REQ_TOKEN: ${{ steps.app-token.outputs.token }}

.github/workflows/jekyll-link-checker.yml:177

• [nitpick] Consider verifying that embedding the token directly within the JSON string does not lead to shell parsing issues, especially if the token could contain unexpected characters. If so, consider a more robust token injection method.

--typhoeus '{"connecttimeout": 10, "timeout": 30, "accept_encoding": "zstd,br,gzip,deflate", "authorization": "Bearer ${{ env.REQ_TOKEN }}" }' \