feat: exit with ExitStatus::Failure on syntax error

[lschuermann]

Summary & Changes

Makes typstyle exit with an ExitStatus::Failure upon encountering a syntax error.

I am integrating it into my editor, and it was quite suprising to me seeing that typstyle will silently ignore erroneous input. This is different from other widespread formatting tools, such as rustfmt.

If there is a good reason to keep the original behavior, I'm happy to put this change behind a command line switch.

Checklist

Before submitting, please ensure you've done the following:

• Updated CHANGELOG.md: Added your changes with examples to the changelog
• Updated documentation: Updated relevant docs, examples, or README
• Added tests: Added tests for new features or bug fixes

Testing

Needs testing.

Additional Notes

[QuadnucYard]

I had discussed with @Enter-tainer about this behavior offline long before. We believed that typstyle was not intended as a syntax checker, so erroneous input can be silently ignored.

Anyway, we can now reconsider the appropriate behavior.