fix: font variant typings (#42760)

Summary:
This PR fixes the typings for `fontVariant` style prop. Flow file has below typings but they were missing in typescript file.

```
  fontVariant?:
  | 'small-caps'
  | 'oldstyle-nums'
  | 'lining-nums'
  | 'tabular-nums'
  | 'common-ligatures'
  | 'no-common-ligatures'
  | 'discretionary-ligatures'
  | 'no-discretionary-ligatures'
  | 'historical-ligatures'
  | 'no-historical-ligatures'
  | 'contextual'
  | 'no-contextual'
  | 'proportional-nums'
  | 'stylistic-one'
  | 'stylistic-two'
  | 'stylistic-three'
  | 'stylistic-four'
  | 'stylistic-five'
  | 'stylistic-six'
  | 'stylistic-seven'
  | 'stylistic-eight'
  | 'stylistic-nine'
  | 'stylistic-ten'
  | 'stylistic-eleven'
  | 'stylistic-twelve'
  | 'stylistic-thirteen'
  | 'stylistic-fourteen'
  | 'stylistic-fifteen'
  | 'stylistic-sixteen'
  | 'stylistic-seventeen'
  | 'stylistic-eighteen'
  | 'stylistic-nineteen'
  | 'stylistic-twenty';
```

## Changelog:

[GENERAL] [ADDED] - Added missing typings for fontVariant style prop.

Pull Request resolved: #42760

Test Plan: Tested manually.

Reviewed By: cortinico

Differential Revision: D53263569

Pulled By: javache

fbshipit-source-id: b127e0377cf9ceb50d094294d188f87a23038e5b

Author: ankit-tailor

packages/react-native/Libraries/StyleSheet/StyleSheetTypes.d.ts

@@ -281,15 +281,35 @@ export type FontVariant =
   | 'oldstyle-nums'
   | 'lining-nums'
   | 'tabular-nums'
-  | 'proportional-nums'
   | 'common-ligatures'
   | 'no-common-ligatures'
   | 'discretionary-ligatures'
   | 'no-discretionary-ligatures'
   | 'historical-ligatures'
   | 'no-historical-ligatures'
   | 'contextual'
-  | 'no-contextual';
+  | 'no-contextual'
+  | 'proportional-nums'
+  | 'stylistic-one'
+  | 'stylistic-two'
+  | 'stylistic-three'
+  | 'stylistic-four'
+  | 'stylistic-five'
+  | 'stylistic-six'
+  | 'stylistic-seven'
+  | 'stylistic-eight'
+  | 'stylistic-nine'
+  | 'stylistic-ten'
+  | 'stylistic-eleven'
+  | 'stylistic-twelve'
+  | 'stylistic-thirteen'
+  | 'stylistic-fourteen'
+  | 'stylistic-fifteen'
+  | 'stylistic-sixteen'
+  | 'stylistic-seventeen'
+  | 'stylistic-eighteen'
+  | 'stylistic-nineteen'
+  | 'stylistic-twenty';
 export interface TextStyleIOS extends ViewStyle {
   fontVariant?: FontVariant[] | undefined;
   textDecorationColor?: ColorValue | undefined;