[ImgBot] Optimize images

*Total -- 531.86kb -> 465.33kb (12.51%)

/plotlyflask_tutorial/static/img/logo.png -- 5.79kb -> 3.44kb (40.55%)
/plotlyflask_tutorial/static/dist/img/favicon.png -- 5.79kb -> 3.44kb (40.55%)
/.github/dash@2x.jpg -- 520.29kb -> 458.45kb (11.89%)

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

Author: ImgBotApp