[ImgBot] Optimize images

*Total -- 292.76kb -> 196.85kb (32.76%)

/images/emailbot.png -- 18.75kb -> 9.89kb (47.27%)
/images/expected-config.png -- 181.37kb -> 115.31kb (36.42%)
/images/emailbot-border.png -- 28.32kb -> 20.18kb (28.73%)
/images/example-button.png -- 56.40kb -> 44.33kb (21.4%)
/images/bothierarchy.png -- 7.92kb -> 7.14kb (9.85%)

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

Author: ImgBotApp