Add a "Writing & Notes" badge to the repository README indicating this repo contains the user's written thoughts, analysis, or notes on various subjects (not planning/task notes).

Use this shields.io badge format:
```markdown
![Writing & Notes](https://img.shields.io/badge/Writing_&_Notes-4A90E2?style=for-the-badge&logo=bookstack&logoColor=white)
```

Add it to the appropriate badges section in the README.