Type definitions have inconsistencies

### Description

Certain type definitions for extendedTheme are inconsistent typings.

### CodeSandbox/Snack link

https://codesandbox.io/s/amazing-meitner-gfmeei?file=/src/App.tsx

### Steps to reproduce

1. Go to 'native-base/lib/typescript/core/extendedTheme.d.ts'
3. Scroll down to 'letterSpacings:{}'
4. See object:
```
letterSpacings: {
xs: string;
sm: string;
md: number; <-- random number type among strings
lg: string;
xl: string;
'2xl': string;
};
```

### NativeBase Version

3.3.3

### Platform

- [ ] Android
- [ ] CRA
- [ ] Expo
- [ ] iOS
- [ ] Next

### Other Platform

_No response_

### Additional Information

You can see in the 'letterSpacings' object that 'md' is a number when all others are strings this works fine if you keep the standard definitions defined by native-base but working with a design system causes issues with token import mapping. It would be nice if the native-base objects contained the same type for all values to keep consistency with design tokens.