[core] Fix docs:start which should start next.js server (#20202)
[core] Fix docs:start which should start next.js server (#20202)


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