[Chore] Bump version to v0.5.1

[bhavnicksm]

This pull request includes a version update for the chonkie project. The version has been incremented from 0.5.0 to 0.5.1 in both the pyproject.toml file and the src/chonkie/__init__.py file.

Version update:

• pyproject.toml: Updated the version field from 0.5.0 to 0.5.1.
• src/chonkie/__init__.py: Updated the __version__ attribute from 0.5.0 to 0.5.1.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

Flag	Coverage Δ
python-3.10	69.76% <100.00%> (ø)
python-3.11	69.76% <100.00%> (ø)
python-3.12	69.76% <100.00%> (ø)
python-3.13	69.76% <100.00%> (ø)
python-3.9	69.75% <100.00%> (ø)

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Files with missing lines	Coverage Δ
src/chonkie/__init__.py	100.00% <100.00%> (ø)