[ImgBot] Optimize images

*Total -- 3,908.88kb -> 3,739.96kb (4.32%)

/issue-17/melonjs.svg -- 3.22kb -> 2.45kb (23.91%)
/issue-19/what-the-filter.png -- 80.58kb -> 69.20kb (14.12%)
/issue-17/color-review.png -- 5.71kb -> 4.94kb (13.54%)
/issue-16/gif-16.gif -- 2,210.20kb -> 2,100.48kb (4.96%)
/issue-17/gif-17.gif -- 1,288.42kb -> 1,250.59kb (2.94%)
/issue-19/gif-19.gif -- 303.57kb -> 295.21kb (2.76%)
/issue-14/tagify.svg -- 11.85kb -> 11.78kb (0.55%)
/issue-16/svgbox.svg -- 5.33kb -> 5.31kb (0.42%)

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Author: ImgBotApp