'inst/doc' files

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, r-lib/actions/setup-pandoc@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

The following actions use a deprecated Node.js version and will be forced to run on node20: actions/checkout@v2, r-lib/actions/setup-pandoc@v1. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/