docs/Tips-and-Tricks: Include Formulae API in Homebrew caching proxy instructions

Expanded section on configuring Homebrew to use a caching proxy or
mirror for both bottles and the Formulae API, including setup instructions.

Include HOMEBREW_BREW_GIT_REMOTE in caching proxy/mirror instructions.
This is specifically _not_ included in the Artifactory example because
I cannot confirm that Artifactory can mirror VCS repos itself.
It can only act as effectively an API to its refs;
it doesn't provide a clone-able URL.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>