[Docs]: GitHub Pages relative links note

[akirataguchi115]

Motivation

When deploying via GitHub Actions and the corresponding guide: https://jekyllrb.com/docs/continuous-integration/github-actions/ the URL navigation doesn't work as it would work locally. Here's an example repository with GitHub Pages deployed: https://github.com/akirataguchi115/blog
Locally /is localhost:4000/
Locally /about is localhost:4000/about.html
on GitHub Pages / is akirataguchi115.github.io/blog/
on GitHub Pages /about is akirataguchi115.github.io/blog/about.html
However GitHub Pages points /pagesto akirataguchi115.github.io/about.html which does not exist.

Suggestion

Add a note in https://jekyllrb.com/docs/continuous-integration/github-actions/ that the navigation created during the tutorial does not work in GitHub Pages.