Add CHANGELOG.md

[rianjs]

Summary

The repository has no CHANGELOG.md file. Users browsing the repo or installing via package managers can't easily see version history.

Recent changes to document

• feat(config): align init/config UX with atlassian-cli patterns (feat(config): align init/config UX with atlassian-cli patterns #44)
• docs: add comprehensive README.md (docs: add comprehensive README.md #42)
• refactor: code simplification and consistency improvements (refactor: code simplification and consistency improvements #40)

Tasks

• Create CHANGELOG.md following Keep a Changelog format
• Document recent changes under [Unreleased] section