Add Cross platform Soroban RPC SDK to docs

[anataliocs]

What problem does your feature solve?

Add Cross platform Soroban RPC SDK written in .NET.

• Complete Soroban RPC Support: Supports all endpoints in the Soroban RPC API
• XDR Serialization: Full XDR encoding and decoding for all Stellar data types
• Type Safety: Strong C# typing for Stellar operations and responses
• Cross-Platform: Works on .NET Core, Unity, MAUI, Tizen and more
• Async First: Fully asynchronous API for responsive applications
• Comprehensive XDR Support: All Stellar XDR types are available
• Automatic Updates: The RPC, XDR and Protobuf (for native) types are automatically generated based on Stellar specifications

What would you like to see?

What alternatives are there?

[ElliotFriend]

Closing as completed: the community C# .NET SDK with full Soroban RPC support (Beans-BV/dotnet-stellar-sdk) is listed on the client SDKs page — which covers what this issue describes. If you meant a different library, please re-file with a link and we'll add it.