It is important to change the style precedence order with the help of the
StyledEngineProvider component, otherwise the internal MUI classes will overwrite
your styles.
module Styles = {
open CssJs
let categoryButton = style([textTransform(#none), justifyContent(#flexStart)])
}
@react.component
let make = () =>
<Mui.StyledEngineProvider injectFirst=true>
<Mui.Button color=Primary classes={root: Styles.categoryButton} onClick=ignore>
{React.string("Hello, BS-CSS & MUI!")}
</Mui.Button>
</Mui.StyledEngineProvider>