Add Unit Test project

[PhilippNaused]

@Lyrcaxis, you said you weren't particular about the choice of framework, so I used TUnit.

[Copilot]

Pull Request Overview

This pull request adds a new unit test project using TUnit for testing the Tokenizer functionality. It also adjusts the PreprocessText method by providing a default parameter for langCode and updates project configuration files accordingly.

• Added default parameter "en-us" to PreprocessText method.
• Configured InternalsVisibleTo in the main project to support unit testing.
• Introduced a new test project with several Tokenizer tests and a CI workflow for building and testing.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
KokoroSharp/Processing/Tokenizer.cs	Updated PreprocessText with a default parameter for langCode
KokoroSharp/KokoroSharp.csproj	Added InternalsVisibleTo for unit testing
KokoroSharp.sln	Included the new KokoroSharp.Tests project in the solution
KokoroSharp.Tests/TokenizerTests.cs	New test file for Tokenizer with various test cases
KokoroSharp.Tests/KokoroSharp.Tests.csproj	New project file for unit tests using TUnit
.github/workflows/tests.yml	New GitHub Actions workflow configuration for build & test

Comments suppressed due to low confidence (2)

KokoroSharp/Processing/Tokenizer.cs:84

• Update the XML documentation for PreprocessText to mention the default value for langCode and any related behavior.

internal static string PreprocessText(string text, string langCode = "en-us") {

KokoroSharp.Tests/TokenizerTests.cs:3

• The namespace 'Kokoro.Tests' does not match the project name 'KokoroSharp.Tests'. Consider renaming it for consistency.

namespace Kokoro.Tests;

[Lyrcaxis]

Nice, let's test!