v0.1.1: bug fix + config file + CI fail threshold

Bug fix:
- Fix _find_unreferenced_components: all_imported_names loop was a no-op,
  causing imported components to be falsely reported as unreferenced.
  Now correctly uses imports.keys() to get all imported names.

Features:
- Add .deadcode.yml config file support (ignore, categories, fail_threshold)
- Add --fail N option to deadcode scan for CI gating (exit 1 if findings >= N)
- Config ignore patterns merged with CLI --ignore flags
- Add pyyaml dependency for YAML config parsing

Docs:
- Fix README: remove false claim about TypeScript compiler API (uses regex)
- Document .deadcode.yml configuration format
- Document --fail option for CI integration

Tests: 39/39 passing (23 original + 16 new)

v0.1.0: Initial release