[ImgBot] Optimize images

*Total -- 568.28kb -> 557.25kb (1.94%)

/assets/img/dflow.svg -- 4.50kb -> 4.39kb (2.5%)
/assets/fonts/glyphicons-halflings-regular.svg -- 106.19kb -> 103.92kb (2.14%)
/assets/fonts/fontawesome-webfont.svg -- 433.96kb -> 425.36kb (1.98%)
/assets/img/bot2.svg -- 3.45kb -> 3.44kb (0.25%)
/assets/img/bot1.svg -- 17.05kb -> 17.02kb (0.17%)
/assets/img/star.svg -- 3.13kb -> 3.13kb (0.12%)

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

Author: ImgBotApp