Fix parsing

[kunitoki]

This pull request introduces a new workaround for parsing C++ translation units on macOS by injecting the system SDK path when needed, and adds comprehensive tests to ensure the robustness of this logic. It also bumps the package version and makes minor documentation updates.

macOS sysroot injection and related test coverage:

• Added logic in parse_translation_unit (in parser.py) to detect when running on macOS without an explicit -isysroot argument, and automatically inject the system SDK path using xcrun to prevent missing C header errors. Handles and silences possible exceptions if xcrun fails or is missing.
• Added a new TestDarwinSysroot test class in test_parser.py to cover all code paths of the sysroot injection logic, including cases where -isysroot is already present, xcrun returns an empty string, or raises errors.

Diagnostics handling:

• Improved diagnostics printing in parse_translation_unit to only print all diagnostics when verbose, but always collect errors for strict mode.

Version and documentation:

• Bumped the package version to 0.22.0 in __init__.py.
• Updated badge URLs in README.md to reflect the new version and minor query parameter changes. [1] [2]