Rationalize example naming and folder structure

**Motivation:**
Current example files and folder structure may be inconsistent or unclear, making it harder for users to discover and navigate them.

This task aims to review and improve:
- Example file naming conventions
- Folder organization within the examples/ directory

The goal is to improve usability and ease of discovery, especially for newcomers exploring features via examples.

**Note:**
- [ ] Avoid naming example files after their corresponding `src` modules (e.g., led.rs, pca9685.rs) to improve file searchability in IDEs.
- [ ] Update the example README file
- [ ] Update the overall README file

**Impact:**
No functional/API impact. This is a user / developer experience improvement.