Add FAQ "Why Homebrew?"

[Ganipotes]

• security : security reviews by Trail of bits
• UX : no need to reboot to install packages, no need to layer it (!= rpm-ostree)

[RoyalOughtness]

also useful, Homebrew has fixed many of the findings already: https://github.com/Homebrew/brew.sh/blob/master/_posts/2024-07-30-homebrew-security-audit.md?plain=1#L24