chore: small cosmetic readme update

Author: nirsky

README.md

@@ -24,7 +24,7 @@ react-native-size-matters provides some simple tooling to make your scaling a wh
 The idea is to develop once on a standard ~5" screen mobile device and then simply apply the provided utils.  
 📖 You can read more about what led to this library on my blog post, which can be found in [this repo](./examples/BlogPost) or at [Medium](https://medium.com/soluto-engineering/size-matters-5aeeb462900a).
 
-## Api
+## API
 ### Scaling Functions
 ```js
 import { scale, verticalScale, moderateScale } from 'react-native-size-matters';