[ImgBot] Optimize images

*Total -- 1,701.27kb -> 1,412.41kb (16.98%)

/dbdiagram.png -- 187.67kb -> 117.01kb (37.65%)
/specs.png -- 314.17kb -> 238.12kb (24.21%)
/board-mobile.png -- 94.09kb -> 72.05kb (23.43%)
/user-profile.png -- 142.76kb -> 111.97kb (21.56%)
/board-grid.png -- 199.50kb -> 168.88kb (15.35%)
/new-board-mobile.png -- 411.39kb -> 378.05kb (8.11%)
/board.png -- 182.04kb -> 168.42kb (7.48%)
/signup.png -- 169.15kb -> 157.42kb (6.93%)
/app/assets/images/trello-logo-vector.svg -- 0.49kb -> 0.49kb (0.2%)

Signed-off-by: ImgBotApp <[email protected]>

Author: ImgBotApp