add: github action for deploy

[netpyoung]

This pr contains github action to generate github pages when push deploy branch.

I'm not sure what kind of method are you using currently build & hosting static web files.

When I translating tryclojure for korean, I used github action & page to deploy site.

• here is korean version : https://lispkorea.github.io/tryclojure-kr/

If you are using service which need to pay to hosting static files it can reduce cost for that except domain name.

ref

• https://docs.github.com/en/actions
• https://github.blog/2009-12-29-bypassing-jekyll-on-github-pages/

[eliascotto]

Thanks for the PR. Korean version looks great.
I'm using Netlify that publishes the website for free. I'll keep the PR open in case I need to publish using github pages.