json.js

exports.translate = function(load) {
  load.source = 'module.exports = ' + load.source + ';';
};

main.js

import data from  './path./to/data.json!';

stealconfig.js

steal.config({
  ext: {
    json: 'path/to/json' // This is the part to your json.js file (above) which is the plugin
  }
});