[ImgBot] Optimize images

*Total -- 89.80kb -> 77.27kb (13.96%)

/Images/Chat_Client_1.png -- 20.00kb -> 16.26kb (18.7%)
/Images/Chat_Server_1.png -- 10.58kb -> 8.94kb (15.53%)
/Images/Chat_Client_2.png -- 16.72kb -> 14.24kb (14.8%)
/Images/Chat_Client_3.png -- 42.50kb -> 37.83kb (11%)

Author: ImgBotApp