Update Homebrew performance comparisons

Hello!

Homebrew has done a lot of work on performance recently which continues unabated. Thanks for helping motivate us!

https://github.com/lucasgelfond/zerobrew#performance-snapshot

Would be nice if this could be updated.

Other nice-to-haves might be to note:

• the Homebrew and Zerobrew version numbers
• if Homebrew is warm or cold
• the download bandwidth, Apple hardware, etc.

for a more like-for-like comparison that's easier to update in future.

If Zerobrew is still 5-20x faster: feel free to keep (or if better increase!) those claims.