dev: publish website via gh-pages branch rather than separate repository

Currently the website generated by this project is published via the separate repository https://github.com/practicalli/clojure-study-group

If this project is viable, add a CI workflow to build the project and publish it via the gh-pages branch.

Delete the https://github.com/practicalli/clojure-study-group repository

Rename this repository to https://github.com/practicalli/clojure-study-group