Optimize tracker.js#118

I read this response on Github, looks promising that still 30%ish can be saved on the script today.

https://github.com/plausible-insights/plausible/issues/52

Absolutely! Some great comments there and I’m all about slimming down the script :)

I released the optimized tracker today. It is 1.2kb on disk, 788B gzipped, 612B w/ brotli compression. Glad to make Plausible even more lightweight than it was before!