add image for REDPACKET.md
add image for REDPACKET.md

wizardguy/ChatKit-OC,ChenYilong/ChatKit-OC,Maru-zhang/ChatKit-OC,Maru-zhang/ChatKit-OC,Maru-zhang/ChatKit-OC,luonaerduo9/ChatKit-OC,leancloud/ChatKit-OC,Maru-zhang/ChatKit-OC