Add RESX migration skill to C# plugin (#2812)

plugins/csharp-dotnet-development/plugin.json

@@ -2,7 +2,7 @@
   "$schema": "https://agent-plugins.org/schemas/1.0.0/plugin.schema.json",
   "name": "csharp-dotnet-development",
   "description": "Essential prompts, instructions, and chat modes for C# and .NET development including testing, documentation, and best practices.",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "author": {
     "name": "Awesome Copilot Community"
   },
@@ -27,7 +27,8 @@
         "./skills/csharp-tunit/",
         "./skills/csharp-xunit/",
         "./skills/dotnet-best-practices/",
-        "./skills/dotnet-upgrade/"
+        "./skills/dotnet-upgrade/",
+        "./skills/resx-source-generator-migration/"
       ]
     }
   }