added changelog.md
added changelog.md

Signed-off-by: gngud21 <f90d56e4178e6def850a47df6c88e9a4491d45e2@naver.com>

4GTommyHarold/COMP4711-lab02,gngud21/COMP4711-lab02,gngud21/COMP4711-lab02,4GTommyHarold/COMP4711-lab02