react: Add JSON test data
react: Add JSON test data

Existing implementations:

* https://github.com/exercism/xfsharp/blob/master/exercises/react/ReactTest.fs
* https://github.com/exercism/xgo/blob/master/exercises/react/react_test.go
* https://github.com/exercism/xnim/blob/master/react/react_test.nim

And an upcoming implementation (that uses these tests):

* https://github.com/exercism/xrust/pull/191

The tests were a union of the existing tests plus a few extras to
provide more gradual steps in the early stages (when still setting up
the input and compute cells).

Closes https://github.com/exercism/todo/issues/135

jmluy/x-common,petertseng/x-common,Vankog/problem-specifications,rpottsoh/x-common,petertseng/x-common,exercism/x-common,jmluy/x-common,ErikSchierboom/x-common,ErikSchierboom/x-common,kgengler/x-common,Vankog/problem-specifications,rpottsoh/x-common,exercism/x-common,kgengler/x-common,jmluy/x-common