docs: add tools table of contents to README

Author: jdevera

README.md

@@ -8,6 +8,15 @@
 
 A collection of git utilities, freshly baked in Go. Vibe-coded.
 
+## Tools
+
+| Tool | Description |
+|------|-------------|
+| [git-explain](#-git-explain) | See contribution status across repositories |
+| [git-id](#-git-id) | Manage identity profiles for multi-account workflows |
+| [git-as](#-git-as) | Run git commands with a specific identity |
+| [gh-as](#-gh-as) | Run GitHub CLI with a specific identity |
+
 ---
 
 ## 🥖 git-explain