Document Homebrew package (#2885)

## Issue Addressed

Resolves #2329

## Proposed Changes

Documents the recently added `lighthouse` Homebrew formula.

## Additional Info

NA


Co-authored-by: Richard Patel <richard@blockdaemon.com>
Co-authored-by: Michael Sproul <micsproul@gmail.com>

book/src/homebrew.md

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+# Homebrew package
+
+Lighthouse is available on Linux and macOS via the [Homebrew package manager](https://brew.sh).
+
+Please note that this installation method is maintained by the Homebrew community.
+It is not officially supported by the Lighthouse team.
+
+### Installation
+
+Install the latest version of the [`lighthouse`][formula] formula with:
+
+```bash
+brew install lighthouse
+```
+
+### Usage
+
+If Homebrew is installed to your `PATH` (default), simply run:
+
+```bash
+lighthouse --help
+```
+
+Alternatively, you can find the `lighthouse` binary at:
+
+```bash
+"$(brew --prefix)/bin/lighthouse" --help
+```
+
+### Maintenance
+
+The [formula][] is kept up-to-date by the Homebrew community and a bot that lists for new releases.
+
+The package source can be found in the [homebrew-core](https://github.com/Homebrew/homebrew-core/blob/master/Formula/lighthouse.rb) repo.
+
+  [formula]: https://formulae.brew.sh/formula/lighthouse