Enable gzip compression in nginx

To increase site performance (and get closer to that juicy 100 performance score in lighthouse), we should enable compression for our static hosts.

Here's a good boilerplate for enabling and configuring gzip in nginx. I wouldn't go as far as recompiling nginx to include better compression tools, like brotli, as that would be a little over the top.

The nginx.conf template of the nginx ansible role has a http_gzip block, which could be replaced by the aforementioned gzip boilerplate.