Fix pkgdown template installation in GitHub Actions

[Copilot]

The pkgdown workflow was failing because the configured template package was not available via install.packages() for the runner's R version. This change switches the workflow to install the template from its source repository before pkgdown::deploy_to_branch() runs.

• Root cause

  • pkgdown requires golemversetemplate via _pkgdown.yml.
  • The workflow attempted to install that package from r-universe, but no compatible build was available for the Actions runner, leaving the template missing at deploy time.

• Workflow change

  • Replace the install.packages() call in .github/workflows/pkgdown.yaml with a direct pak::pak() install from ThinkR-open/golemversetemplate.
  • Keep the rest of the deployment flow unchanged.

• Result

  • The workflow now resolves the pkgdown template independently of repository binary availability for a specific R version.

- name: Deploy package
  run: |
    Rscript -e 'pak::pak("ThinkR-open/golemversetemplate")'
    git config --local user.name "$GITHUB_ACTOR"
    git config --local user.email "$GITHUB_ACTOR@users.noreply.github.com"
    Rscript -e 'pkgdown::deploy_to_branch(new_process = FALSE)'