[docs] Add OpenCollective gold sponsors manually (#13806)
[docs] Add OpenCollective gold sponsors manually (#13806)

* Add OpenCollective gold sponsors manually

* Try centering the logos

* Update folling review

mui-org/material-ui,kybarg/material-ui,callemall/material-ui,Kagami/material-ui,rscnt/material-ui,Kagami/material-ui,mui-org/material-ui,oliviertassinari/material-ui,callemall/material-ui,mui-org/material-ui,kybarg/material-ui,oliviertassinari/material-ui,lgollut/material-ui,mbrookes/material-ui,mbrookes/material-ui,allanalexandre/material-ui,rscnt/material-ui,kybarg/material-ui,callemall/material-ui,Kagami/material-ui,callemall/material-ui,kybarg/material-ui,mbrookes/material-ui,rscnt/material-ui,Kagami/material-ui,oliviertassinari/material-ui