Examples with Simnibs for tms/tdcs

[maedoc]

The purpose of this issue is to propose the creation of a comprehensive example that demonstrates how to use the vbjax library in conjunction with simnibs for simulating models with transcranial magnetic stimulation (TMS).

1. Comprehensive Example: A step-by-step guide demonstrating the integration process.
2. Use Case Scenarios: Examples of common use cases in TMS simulations using both vbjax and simnibs.
3. Documentation: Detailed documentation explaining each step and the underlying principles.
4. Code Snippets: Practical code examples that users can easily adapt for their specific needs.
5. Validation: Showcase a comparison of results with and without the integration to highlight the benefits.

@i-Zaak