[ImgBot] Optimize images

*Total -- 6,718.40kb -> 6,466.02kb (3.76%)

/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-20/gif-20.gif -- 2,814.85kb -> 2,731.37kb (2.97%)
/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%)

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

Author: ImgBotApp