[ImgBot] Optimize images

*Total -- 91.95kb -> 69.17kb (24.78%)

/images/springmessage/image-20200305085845017.png -- 13.35kb -> 9.72kb (27.18%)
/images/springmessage/image-20200305090846313.png -- 9.58kb -> 7.13kb (25.59%)
/images/springmessage/image-20200304092154712.png -- 26.43kb -> 19.85kb (24.87%)
/images/springmessage/image-20200305085013723.png -- 26.26kb -> 19.84kb (24.45%)
/images/springmessage/image-20200304085303580.png -- 16.33kb -> 12.62kb (22.7%)

Signed-off-by: ImgBotApp <ImgBotHelp@gmail.com>

Author: ImgBotApp