Implement SimpleNote CLI - full Commander.js CLI

- Commander.js-based CLI with subcommands
- Document commands: list, get, create, update, delete, export, add-tags
- Library commands: list, get, create, tree
- Tag commands: list, docs
- Auth commands: login, status
- Axios-based API client with error handling
- Config loader for ~/.config/simplenote/config.json
- Chalk for colored output

.env.example

@@ -0,0 +1,3 @@
+# SimpleNote CLI Configuration
+SIMPLENOTE_API_URL=http://localhost:3000/api/v1
+SIMPLENOTE_TOKEN=snk_your_token_here