feat: add Homebrew tap automation and update install docs

Add GitHub Actions workflow that auto-updates the Homebrew formula
in coderabbitai/homebrew-tap on each new release. Update README to
promote `brew install git-gtr` as the primary macOS install method.

Closes #92

Author: helizaga

.github/workflows/homebrew.yml

@@ -0,0 +1,25 @@
+name: Update Homebrew Formula
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  homebrew:
+    name: Bump Homebrew formula
+    runs-on: ubuntu-latest
+    if: ${{ !github.event.release.prerelease }}
+    steps:
+      - uses: mislav/bump-homebrew-formula-action@v3
+        with:
+          formula-name: git-gtr
+          formula-path: Formula/git-gtr.rb
+          homebrew-tap: coderabbitai/homebrew-tap
+          tag-name: ${{ github.event.release.tag_name }}
+          create-pullrequest: false
+          commit-message: |
+            {{formulaName}} {{version}}
+
+            Automated update from https://github.com/coderabbitai/git-worktree-runner
+        env:
+          COMMITTER_TOKEN: ${{ secrets.HOMEBREW_TAP_TOKEN }}

README.md

@@ -42,7 +42,14 @@
 
 ## Quick Start
 
-**Install:**
+**Homebrew (macOS):**
+
+```bash
+brew tap coderabbitai/tap
+brew install git-gtr
+```
+
+**Script installer (macOS / Linux):**
 
 ```bash
 git clone https://github.com/coderabbitai/git-worktree-runner.git
@@ -51,13 +58,7 @@ cd git-worktree-runner
 ```
 
 <details>
-<summary><b>Manual installation options</b></summary>
-
-**macOS (Apple Silicon with Homebrew):**
-
-```bash
-ln -s "$(pwd)/bin/git-gtr" "$(brew --prefix)/bin/git-gtr"
-```
+<summary><b>Other installation options</b></summary>
 
 **macOS (Intel) / Linux:**