docs: qualify brew install, clarify per-package apk/pacman signing brew install silo collides with homebrew-core's own silo formula once tapped; needs the full tap/formula form. Also documents that silo only signs the apk index / pacman database, never individual package files, and what to do (and which key to reuse) if a client needs per-package signatures instead.
Add Installation page: deb/rpm/apk/pacman packages and Homebrew tap