[ImgBot] Optimize images

*Total -- 1,483.02kb -> 115.83kb (92.19%)

/assets/chars_and_branchname.gif -- 1,324.54kb -> 97.60kb (92.63%)
/assets/pull.gif -- 158.47kb -> 18.23kb (88.5%)

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

Author: ImgBotApp