Add Csharp snippets extension (#3940)

A collection of C# code snippets

### Features
- 100+ snippets covering various C# development scenarios
- Support for ASP.NET Core (MVC, Razor Pages, Minimal APIs)
- CQRS/MediatR patterns for clean architecture
- Testing frameworks (xUnit, NUnit, MSTest)
- Mocking with Moq
- Common boilerplates for classes, interfaces, controllers, and more

---------

Co-authored-by: Finn Evers <[email protected]>

Author: kenBinary

.gitmodules

@@ -582,6 +582,10 @@
 	path = extensions/csharp
 	url = https://github.com/zed-extensions/csharp.git
 
+[submodule "extensions/csharp-snippets"]
+	path = extensions/csharp-snippets
+	url = https://github.com/kenBinary/csharp-zed-snippets.git
+
 [submodule "extensions/cspell"]
 	path = extensions/cspell
 	url = https://github.com/mantou132/zed-cspell

extensions.toml

@@ -586,6 +586,10 @@ version = "0.0.1"
 submodule = "extensions/csharp"
 version = "0.1.3"
 
+[csharp-snippets]
+submodule = "extensions/csharp-snippets"
+version = "0.1.0"
+
 [cspell]
 submodule = "extensions/cspell"
 version = "0.0.6"