Make the React example less esoteric

[insin]

I've never seen React code which uses curly braces the way they're used in this example.

This change doesn't put curly braces on the same line as parent elements and uses the arrow function's implicit return when mapping the list, while retaining the other decisions which have been made:

• pointless, line-eating ( ) wrappers (which do seem to be in common use)
• using a ternary
• spacing of the ternary parts