Body of Influence (BOI) Example

### 📝 Description of the feature

I would like to ask you if it's possible to extend examples to explain using Body of Influence (BOI) in pyPrimeMesh. Some extensions to the F1 wing, or toy car example, create a BOI for defining the size of the element in the BOI volume. How to create BOI and integrate sizing specification.

Thank you for the nice project.

### 💡 Steps for implementing the feature

_No response_

### 🔗 Useful links and references

_No response_

Review the existing F1 wing and toy car examples in pyPrimeMesh, then identify how they create geometry and apply sizing specifications. Confirm the documented BOI creation and integration steps, and consider the work complete when an example clearly shows creating a BOI and defining element size within its volume.

Written by the indexing model from the issue text.