docs: add v0.6.0 changelog entry

[Copilot]

Prepare the v0.6.0 release notes by adding a changelog entry that rolls up the user-visible changes merged in PRs #25, #32/#33, #35, and #36. This updates the release history so the upcoming tag has a complete, scan-friendly summary.

• Release notes

  • add a new 0.6.0 section dated 2026-04-07
  • group the release into Added, Changed, and Fixed
  • summarize the shipped changes around key binding customization, macOS voice selection, security/support docs, and CI lint enforcement

• Link maintenance

  • move Unreleased to compare from v0.6.0
  • add the 0.6.0 compare link against v0.5.2
  • restore the missing 0.5.2 reference link for consistency at the bottom of the changelog

• Changelog shape

  • keep the existing release-note format intact so future releases can continue appending entries without restructuring the file

## [0.6.0] - 2026-04-07

### Added
- ホーム設定から開ける Key Bindings Editor を追加し、コンテキストごとのショートカットを記録・編集・クリア・リセットできるようにしました。

[Unreleased]: https://github.com/harumiWeb/eitango/compare/v0.6.0...HEAD
[0.6.0]: https://github.com/harumiWeb/eitango/compare/v0.5.2...v0.6.0

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[devin-ai-integration]

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