use custom font in material ui code example

Example: change font of all material ui typography

const theme = createMuiTheme({
  typography: {
    fontFamily: 'Raleway, Arial',
  },
  overrides: {
    MuiCssBaseline: {
      '@global': {
        '@font-face': [raleway],
      },
    },
  },
});

// ...
return (
  <ThemeProvider theme={theme}>
    <CssBaseline />
    {children}
  </ThemeProvider>
);