Support building site locally with Docker

[kwin]

Instead of a complicated installation/compilation of all dependencies locally one can use an existing docker image to run the Jekyll build locally.

There are some hints in https://github.com/github/pages-gem or https://github.com/peteretelej/jekyll-container on how this may be achieved.

[kwin]

The image from https://github.com/BretFisher/jekyll-serve seems to support multiple architectures. Not sure though how close this is to the GitHub Pages tool versions (https://pages.github.com/versions/).

[kwin]

There is also docker support from https://github.com/github/pages-gem?tab=readme-ov-file#docker.