add CHANGELOG.md
add CHANGELOG.md


Former-commit-id: 455d8507494b3358bd049fdfb42649b50d6a5b2a [formerly 130ae894fbe6ab6f2d0383a32ded61544f048e6f]
Former-commit-id: 86b301e7b04ac2b6021f2e59dcba4b84b6f73451
simomarsili/elss