Fix duplicate source generator loading by using versioned roslyn3.10/ analyzer path

Co-authored-by: atifaziz <20511+atifaziz@users.noreply.github.com>

Author: Copilot

src/DocoptNet/DocoptNet.csproj

@@ -73,8 +73,11 @@ Portions Copyright (C) West Wind Technologies, 2008.
   </ItemGroup>
 
   <ItemGroup>
-    <!-- Package the generator in the analyzer directory of the nuget package -->
-    <None Include="$(OutputPath)\netstandard2.0\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
+    <!-- Package the generator in the analyzer directory of the nuget package.
+         Using a versioned roslyn3.10/ folder instead of the unversioned cs/ path ensures the SDK
+         selects only the best-matching Roslyn variant (3.10 baseline or 4.4) rather than loading both.
+         See: https://github.com/dotnet/sdk/issues/20355 -->
+    <None Include="$(OutputPath)\netstandard2.0\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/roslyn3.10/cs" Visible="false" />
     <!-- Package the Roslyn 4.4 variant of the generator -->
     <None Include="$(_Roslyn44AnalyzerDir)$(Configuration)/netstandard2.0/$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/roslyn4.4/cs" Visible="false" />
     <!--