Ember: show how to use app.toTree() to copy assets instead of a package script

[tomwayson]

A slightly more Ember-ish way to copy the assets would be to include them in app.toTree().

I'm thinking of trying the following and if it works Adding CSS and Adding Icons README sections could be combined into a single section w/ the following snippet:

// ember-cli-build.js
const path = require('path');
const EmberApp = require('ember-cli/lib/broccoli/ember-app');
const Funnel = require('broccoli-funnel');

module.exports = function(defaults) {
  let app = new EmberApp(defaults, {});

  // tell the app to import the global stylesheet
  app.import('node_modules/@esri/calcite-components/dist/calcite/calcite.css');

  // copy the assets to the app's public folder
  const calciteComponentsAssetsTree = new Funnel(path.dirname(require.resolve('@esri/calcite-components/dist/calcite/calcite.css')), {
    files: ['assets']
  });

  return app.toTree(calciteComponentsAssetsTree);
};

I've copied that from our app where I've verified that it works w/ development builds. However, I have yet to verify it in a production build that does fingerprinting and prepending w/ CDN URLs. If there were any problems w/ fingerprinting and prepending, they would apply to the copy script too, so I figure we might as well try it here.

[paulcpederson]

Fixed as part of #6