docs(Echo): update emoji skin tone in contribution section

Adjust the 'pointing hand' emoji in README.md to use a light skin tone variant (👉🏻) for visual consistency with recent documentation updates. This cosmetic change aligns with ongoing efforts to refine contribution guidelines while maintaining focus on Echo's role in Tauri event orchestration between Mountain and Wind layers.

Refs #ef7c05287f4b6f55396b18fd4565ef5ca35bcbe5

Author: NikolaRHristov

README.md

@@ -222,7 +222,7 @@ levels.
 | **Expert Tuning**  | Build a `criterion` benchmark suite; implement CPU pinning. |
 | **Advanced Logic** | Introduce an anti-starvation mechanism for tasks.           |
 
-**Interested in tackling one of these challenges?** 👉
+**Interested in tackling one of these challenges?** 👉🏻
 
 - **[Check out our full TODO](docs/TODO.md)** for challenges!
 - **[Follow our Contribution Guide](CONTRIBUTING.md)** to get started!