2020-11-02: add search interface

[fmichonneau]

Ctrl+F works ok but it might be worth looking into other solutions?

[baileythegreen]

Some solutions use plugins that apparently don't play well with GitHub Pages, but this one says it doesn't require plugins: Tipue. It's archived, but might be a start?

Or there are Google site searches, which might be less pretty, but unarchived.

[agnescameron]

Hi, I'd be interested to help with this! I've used Simple Jekyll Search before, I believe it works fine with GH Pages. It might require a bit of adaption as the searched objects are individual pages, but I'd imagine most of the code would be reusable (the repo contains both the minified release and the source code).