feat: enable 'fast' optional dependency now that json2xml-rs is published

Users can now install with Rust acceleration via:
  pip install json2xml[fast]

Author: vinitkumar

pyproject.toml

@@ -50,11 +50,7 @@ include = ["json2xml"]
 test = [
     "pytest>=8.4.1",
 ]
-# Note: The 'fast' extra will be available after json2xml-rs is published to PyPI.
-# For now, install the Rust extension separately:
-#   cd rust && pip install -e .
-# Then the dicttoxml_fast module will automatically use the Rust backend.
-# fast = ["json2xml-rs>=0.1.0"]
+fast = ["json2xml-rs>=0.1.0"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]