Add your json to projects and use ajax
I wrote this tutorial awhile ago, it has the json in projects files, it uses ajax, pretty straight forward really. I know it was to actually use the data in array, but how I got the data into array is what you want to look at.
Edit: just took screenshot
Now you have your array you need to save it to webstorage
[attachment=0:380h8rm7][/attachment:380h8rm7]
Ingamedata is the name of my array in this example