Saves the values in the structure 'data' to a file using JSON format.
Example:
data.name = 'chair';
data.color = 'pink';
data.metrics.height = 0.3;
data.metrics.width = 1.3;
saveJSONfile(data, 'out.json');

Output 'out.json':
{
"name" : "chair",
"color" : "pink",
"metrics" : {
"height" : 0.3,
"width" : 1.3
}
}