TypeScript Typings - WithWidthEnhancement width should be a string or enum

[vyrotek]

Problem description

@sebald I believe width is supposed to be a string or enum and not a number;

  export interface WithWidthEnhancement {
    width: number;
  }

The withWidth.js implementation seems to provide the following possible values.
xs | xs | sm | md | lg | xl

[oliviertassinari]

Sounds correct, feel free to fix the typescript typings.

[vyrotek]

I just saw there's a Breakpoint type. Would it make sense to use that @sebald?

[sebald]

@vyrotek yup, exactly :)