docs: update comparisons table to reference whodunit-chronicles for c…

…hange history

  Update README comparisons section to indicate that change history
  functionality is available via the complement gem whodunit-chronicles,
  maintaining Whodunit's focus on lightweight user tracking while
  providing a path for users who need full audit trails.

feat: improve the `whodunit install` experience

- `whodunit install` now prompts to automatically add `Whodunit::Stampable` to `ApplicationRecord` for convenient all-model stamping
- Detailed explanations and examples for each configuration option in generated initializer
- instructions displayed after gem installation via `bundle add whodunit`
- Full test suite for ApplicationRecord integration with edge case handling

feat: bump minor release version to 0.2.0

style: fix rubocop offenses

fix: bump to actions/download-artifact@v4