chore: update README.md to include instructions for installing via Homebrew (#3172)

Author: ke4qqq

README.md

@@ -4,6 +4,7 @@
 
 - **macOS**:
   - **DMG**: [Download now](https://desktop-release.q.us-east-1.amazonaws.com/latest/Amazon%20Q.dmg)
+  - **HomeBrew**: ```brew install --cask amazon-q ```
 - **Linux**:
   - [Ubuntu/Debian](https://docs.aws.amazon.com/amazonq/latest/qdeveloper-ug/command-line-installing.html#command-line-installing-ubuntu)
   - [AppImage](https://docs.aws.amazon.com/amazonq/latest/qdeveloper-ug/command-line-installing.html#command-line-installing-appimage)