Propose MIT license and refresh README

[hvboq]

Summary

This PR proposes adopting the MIT License for this repository and refreshes the README so users can understand the project setup more easily.

Changes included:

• Add a standard MIT LICENSE file using joshfreitas1984 and contributors as the copyright holder line.
• Add PackageLicenseExpression=MIT to the plugin project metadata.
• Rewrite the README with clearer endpoint, installation, configuration, override file, glossary, prompt tuning, build/test, and current project notes sections.
• Document the current environment-dependent prompt tests and release build caveats so contributors know what to expect.

Why

The upstream repository currently does not expose a detected license through GitHub metadata. Adding an explicit license removes ambiguity for users and contributors about allowed use, modification, and redistribution.

Validation

• git diff --check passed with no whitespace errors.
• dotnet build XUnity.AutoTranslate.LlmTranslators.sln -c Debug passed.

Known existing issues observed while validating:

• dotnet build XUnity.AutoTranslate.LlmTranslators.sln -c Release currently fails in the existing ILRepack.MSBuild.Task merge step on the local .NET SDK.
• dotnet test XUnity.AutoTranslate.LlmTranslators.sln -c Debug --no-build currently fails because one prompt fixture is missing under TestOutput and the Ollama prompt test expects a local Ollama server on localhost:11434.
• Restore/build emits an existing high-severity warning for YamlDotNet 4.2.1.

[hvboq]

Update: this change has also been merged into the hvboq fork's master branch for immediate use there. The upstream PR remains open and ready for review to propose adopting the MIT License and the README improvements in the original repository.

[hvboq]

Superseded by #14. The MIT license proposal and README refresh have been folded into the existing LM Studio PR, so this separate PR is being closed to avoid duplicate review.

[hvboq]

Closing as superseded by #14, which now includes these changes.