Bump Microsoft.NET.Test.Sdk from 18.3.0 to 18.4.0 - #69

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/checkout@v4, actions/setup-dotnet@v4. Actions will be forced to run with Node.js 24 by default starting June 2nd, 2026. Node.js 20 will be removed from the runner on September 16th, 2026. Please check if updated versions of these actions are available that support Node.js 24. To opt into Node.js 24 now, set the FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true environment variable on the runner or in your workflow file. Once Node.js 24 becomes the default, you can temporarily opt out by setting ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION=true. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

- Add lib or ref assemblies for the netstandard2.0 target framework

Some target frameworks declared in the dependencies group of the nuspec and the lib/ref folder do not have exact matches in the other location. Consult the list of actions below:

`Exception` is a reserved exception type

This compiler extension should not be implemented in an assembly containing a reference to Microsoft.CodeAnalysis.Workspaces. The Microsoft.CodeAnalysis.Workspaces assembly is not provided during command line compilation scenarios, so references to it could cause the compiler extension to behave unpredictably. (https://github.com/dotnet/roslyn/blob/main/docs/roslyn-analyzers/rules/RS1038.md)

Argument of type 'ImmutableDictionary<string, string>' cannot be used for parameter 'properties' of type 'ImmutableDictionary<string, string?>' in 'Diagnostic Diagnostic.Create(DiagnosticDescriptor descriptor, Location? location, ImmutableDictionary<string, string?>? properties, params object?[]? messageArgs)' due to differences in the nullability of reference types.

Argument of type 'ImmutableDictionary<string, string>' cannot be used for parameter 'properties' of type 'ImmutableDictionary<string, string?>' in 'Diagnostic Diagnostic.Create(DiagnosticDescriptor descriptor, Location? location, ImmutableDictionary<string, string?>? properties, params object?[]? messageArgs)' due to differences in the nullability of reference types.

Dereference of a possibly null reference.

Argument of type 'ImmutableDictionary<string, string>' cannot be used for parameter 'properties' of type 'ImmutableDictionary<string, string?>' in 'Diagnostic Diagnostic.Create(DiagnosticDescriptor descriptor, Location? location, ImmutableDictionary<string, string?>? properties, params object?[]? messageArgs)' due to differences in the nullability of reference types.

Dereference of a possibly null reference.