v5.18.0
[website] Link Discord in footer (#38369)
[system] Fix various issues reported by using @mui/styled-engine-sc (#29035)
[docs] More general docs polishing (#30371)
[website] Add product core page (#27952)
[website] Link mui-x Stack Overflow in footer link (#37509)
[docs-infra] Adjust the website & docs footer (#39810)
[website] Add content about the Sync plugin in the Material UI page (@danilo-leal) (#42074)