Fix Windows build: read package files using UTF-8 in setup.py (resolves UnicodeDecodeError on 3.0.0)

[BruRdgz]

Closes #306

Summary

• Installing cloudscraper 3.0.0 from the Git tag on Windows failed during the PEP 517 build with a UnicodeDecodeError due to default cp1252 decoding.
• This PR forces UTF-8 when reading package files in setup.py, unblocking builds/installs on Windows.

Changes

• setup.py: read cloudscraper/init.py and README.md with encoding="utf-8".
  • No behavioral/runtime changes.
  • No dependency changes.

Testing

• Environment: Windows 11, Python 3.13, pip 25.2, build 1.2+, Poetry 2.1.4.
• Built artifacts locally:
  • python -m build → produced sdist (.tar.gz) and wheel (.whl).
• Verified installation paths:
  • Wheel: python -m pip install dist/cloudscraper-3.0.0-py3-none-any.whl
  • sdist (PEP 517 path): python -m pip install --no-binary :all: dist/cloudscraper-3.0.0.tar.gz
• Runtime check:
  • python -c "import cloudscraper; print(cloudscraper.__version__)" → 3.0.0
• Also validated install via Poetry in a downstream project from the Git ref.

[BruRdgz]

It was incredibly trivial, so I went ahead and wrote the fix myself for convenience's sake.
Do feel free to test those changes locally.
Let me know if there's any issues.