Add support for hosting of HTML code on GitHub pages

[zhaojj2209]

Currently, code written within the HTML chapter is rendered in an <iframe> component within the Source Academy itself. It would be great if students are able to deploy code written directly to GitHub pages.

Potential security concerns would need to be explored.

[RichDom2185]

Perhaps this can be paired together with the long-stale GitHub integration feature. If a user is working on HTML, and saves the code to GitHub, they'll be given an option to also deploy it at the same time (to their own repository and GitHub Pages).