Add note about style and weight

Author: ahocevar

README.md

@@ -1,6 +1,8 @@
 # Mapbox to CSS Font
 
-Utility to convert Mapbox GL Style font names to CSS compatible font definitions.
+Utility to convert Mapbox GL Style fontstacks or fonts names to CSS compatible font definitions.
+
+For fontstacks, the style and weight of the primary font (first font in the fontstack) will also be used for the fallback fonts.
 
 The ["Klokantech Noto Sans"](https://github.com/klokantech/klokantech-gl-fonts) font is recognized and returned as "Noto Sans", so it can be loaded as web font from Google fonts.
 
@@ -16,7 +18,7 @@ parseFont('Open Sans Regular', 16);
 
 **Parameters**
 
--  `font` **[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** Mapbox GL Style font name, e.g. `'Open Sans Regular'`.
+-  `fonts` **[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)|[Array(https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)]<[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)>** Mapbox GL Style fontstack or single font, e.g. `['Open Sans Regular', 'Arial Unicode MS Regular']` or `'Open Sans Regular'`.
 
 -  `size` **[number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** Font size in pixels.