Define the meaning of the term camel-case in the JSON Style Guide

The [JSON Style Guide](https://google.github.io/styleguide/jsoncstyleguide.xml) says that _property names must be camel-cased_.

There's no definition of the term given. The [Wikipedia](https://en.wikipedia.org/wiki/Camel_case) article shows that there are many variations of camel case, especially with the first letter capitalized. However, the examples given suggest that actually lower camel case is meant.