[core] Export TypographyVariant type (#19598)

Author: aleccaputo

packages/material-ui/src/styles/index.d.ts

@@ -6,7 +6,7 @@ export {
   SimplePaletteColorOptions,
 } from './createPalette';
 export { default as createStyles } from './createStyles';
-export { TypographyStyle } from './createTypography';
+export { TypographyStyle, Variant as TypographyVariant } from './createTypography';
 export { default as makeStyles } from './makeStyles';
 export { default as responsiveFontSizes } from './responsiveFontSizes';
 export { ComponentsPropsList } from './props';