[ImgBot] Optimize images

*Total -- 40.48kb -> 21.22kb (47.58%)

/img/Tezos_Logo-Colored.png -- 8.99kb -> 3.75kb (58.31%)
/img/Polygon_Logo-Colored.png -- 9.61kb -> 4.40kb (54.25%)
/img/Devfolio_Logo-Colored.png -- 8.22kb -> 4.03kb (50.96%)
/img/Filecoin Coloured White Text.png -- 6.63kb -> 3.72kb (43.89%)
/img/Celo Logo Color.png -- 7.03kb -> 5.32kb (24.29%)

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

Author: ImgBotApp