Add TextDecoder polyfill with tests

[CedricGuillemet]

Used by GaussianSplatting for parsing ply/compressed ply headers

[Copilot]

Pull request overview

Adds a TextDecoder polyfill to the JsRuntimeHost polyfills set so GaussianSplatting can parse PLY / compressed PLY headers in environments lacking a native TextDecoder.

Changes:

• Introduce new Polyfills/TextDecoder library and CMake option JSRUNTIMEHOST_POLYFILL_TEXTDECODER.
• Register the polyfill in unit test runtime initialization.
• Add mocha tests covering basic TextDecoder.decode() behavior for Uint8Array and ArrayBuffer.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
Tests/UnitTests/Shared/Shared.cpp	Initializes the new TextDecoder polyfill in the JS test runtime.
Tests/UnitTests/Scripts/tests.ts	Adds mocha coverage for basic TextDecoder.decode() usage.
Tests/UnitTests/CMakeLists.txt	Links UnitTests target against the new TextDecoder library.
Polyfills/TextDecoder/Source/TextDecoder.cpp	Implements the TextDecoder global and decode() in C++ via N-API.
Polyfills/TextDecoder/Include/Babylon/Polyfills/TextDecoder.h	Declares the polyfill Initialize entry point.
Polyfills/TextDecoder/CMakeLists.txt	Adds build target for the TextDecoder polyfill.
Polyfills/CMakeLists.txt	Adds conditional subdirectory inclusion for TextDecoder.
CMakeLists.txt	Adds JSRUNTIMEHOST_POLYFILL_TEXTDECODER option.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.