feat: add version.json to match go-multicodec

[sumanjeet0012]

Closes #44.

What was changed:

• Added version.json at the repository root containing {"version": "v1.0.0"}.
• Added a [[tool.bumpversion.files]] entry to pyproject.toml so bump-my-version automatically keeps version.json in sync with pyproject.toml and multicodec/__init__.py on every release.

Why the change was needed:

• go-multicodec ships a version.json file used by ecosystem tooling to track version compatibility across implementations. py-multicodec was the only implementation missing this file, creating an inconsistency in the multiformats ecosystem.

How it was verified:

• Ran pre-commit run --all-files (ruff lint, ruff format, pyupgrade, mypy — all passed).
• Ran pytest tests — all 689 tests passed.
• Confirmed the check-toml pre-commit hook validates the updated pyproject.toml successfully.