Access keys for certain shortcuts

[This person's](https://github.com/lilianweng/lilianweng.github.io/blob/master/posts/2018-02-19-rl-overview/index.html) [blog](https://lilianweng.github.io/posts/2018-02-19-rl-overview/) has certain access keys for certain actions built into his blog. For example, `Alt + G` is scroll-to-top, `Alt + /` is search, etc.

Figure out how to do the same thing in Jekyll.