[ImgBot] Optimize images (#88)

*Total -- 728.02kb -> 514.23kb (29.37%)

/static/img/Stirling_PDF_App_Icon_-_Favicon_2-f8d8fab3.png -- 12.11kb -> 5.90kb (51.31%)
/static/img/mac-security-allow.png -- 381.74kb -> 256.66kb (32.77%)
/static/img/Group_154-d473d170.png -- 1.86kb -> 1.30kb (30.08%)
/static/img/mac-installer.png -- 177.31kb -> 125.16kb (29.41%)
/static/img/mac-app-blocked.png -- 72.03kb -> 57.45kb (20.25%)
/static/img/promo-footer-dark.jpg -- 31.95kb -> 25.66kb (19.69%)
/static/img/Group_163-62ccf9fd.png -- 51.02kb -> 42.10kb (17.48%)

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

Author: imgbot[bot]