Add codecov badge in README.md
Add codecov badge in README.md

imaNNeoFighT/fl_chart,imaNNeoFighT/fl_chart,imaNNeoFighT/fl_chart,imaNNeoFighT/fl_chart,imaNNeoFighT/fl_chart,imaNNeoFighT/fl_chart,imaNNeoFighT/fl_chart