docs: rewrite compliance page with conversational tone

Completely rewrote the compliance page to be more engaging and informative:
- Opens with the "why" - explaining why compatibility matters with a concrete example
- Discusses the three compliance tracks with context
- Deep dive on NEP 50 type promotion (the biggest NumPy 2.0 change)
- Explains "why it's hard" for missing features (complex, datetime, strings)
- Conversational explanations for each section
- Real code examples showing NumPy vs NumSharp behavior
- Honest about limitations (linear algebra stubs, F-order)
- Clear call to action for contributors

The goal is to help readers understand not just "what" but "why" NumSharp
behaves the way it does and where we're headed.

Author: Nucs