[ImgBot] Optimize images (#20)

*Total -- 279.38kb -> 235.87kb (15.57%)

/images/sample-io-insights.svg -- 39.02kb -> 29.88kb (23.43%)
/images/sample-io-insights-issues.svg -- 29.75kb -> 22.87kb (23.15%)
/images/sample-io-insights-verbose.svg -- 152.37kb -> 128.50kb (15.67%)
/images/drishti-logo.png -- 58.23kb -> 54.63kb (6.18%)

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

Author: jay-tau