Restore the missing picture of CONTRIBUTING.md file
Restore the missing picture of CONTRIBUTING.md file

Signed-off-by: Steven Zou <5c7d09ecc61eee689df7048be4e7fb1d1e0b8ebc@vmware.com>

steven-zou/harbor,steven-zou/harbor,wy65701436/harbor,wy65701436/harbor,reasonerjt/harbor,reasonerjt/harbor,wy65701436/harbor,reasonerjt/harbor,steven-zou/harbor,wy65701436/harbor,reasonerjt/harbor,wy65701436/harbor,reasonerjt/harbor,steven-zou/harbor,steven-zou/harbor,steven-zou/harbor,reasonerjt/harbor,wy65701436/harbor