docs: add Homebrew installation instructions

Add Homebrew tap installation as the primary installation method
in the README, making it easier for users to install the binary
without needing to build from source.

Also reorganize Requirements section to clarify that Go is only
needed for building from source, not for using the binary.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: timvw

README.md

@@ -20,6 +20,13 @@ Inspired by [haacked/dotfiles/tree-me](https://github.com/haacked/dotfiles/blob/
 
 ## Installation
 
+### Homebrew (macOS and Linux)
+
+```bash
+brew tap timvw/tap
+brew install wt
+```
+
 ### From Source
 
 ```bash
@@ -143,8 +150,11 @@ just build-all # Cross-compile for multiple platforms
 ## Requirements
 
 - Git (obviously)
-- Go 1.21+ (for building from source)
 - `gh` CLI (optional, only needed for `wt pr` command)
+
+### For Building from Source
+
+- Go 1.21+
 - `just` (optional, for using the justfile)
 
 ## How It Works