[ImgBot] Optimize images

*Total -- 351.85kb -> 293.86kb (16.48%)

/apps/sticky-notes/img/pin.png -- 4.40kb -> 1.17kb (73.36%)
/apps/static/img/fe-128.png -- 1.90kb -> 1.00kb (47.15%)
/apps/sticky-notes/img/delete.png -- 2.54kb -> 1.51kb (40.49%)
/apps/options/menu-bg.png -- 37.42kb -> 29.64kb (20.78%)
/apps/sticky-notes/img/save.png -- 2.20kb -> 1.78kb (19.36%)
/apps/static/screenshot/menu.png -- 129.21kb -> 105.66kb (18.22%)
/apps/json-format/json-demo.jpg -- 89.46kb -> 75.91kb (15.15%)
/apps/static/screenshot/wx-qrcode-fehelper-group.png -- 35.39kb -> 30.73kb (13.17%)
/apps/sticky-notes/img/time.png -- 1.13kb -> 1.02kb (9.28%)
/apps/static/screenshot/wx-private-qrcode.png -- 48.20kb -> 45.43kb (5.75%)