GitHub Action to Generate Website and Commit to Repo

[humphd]

Similar to #3, we need a way to generate an HTML page that uses all of the optimized images. Once it has been created, we need to re-commit everything in the Actions filesystem back to the repo's gh-pages branch (i.e., we want the built web site to be put into the gh-pages branch).

[saminarp]

I would like to give this issue a try.