Add images attribute

[derrickmar]

The purpose of adding the image attribute is so that one of the tests in controllerSpecs.js does not fail in step_10.ngdoc when we add $scope.mainImageUrl = data.images[0]; to PhoneDetailCtrl.

[mary-poppins]

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[derrickmar]

Hi Mary. Apologies, should have read the Contributing.md first. I submitted a form for CLA.

[petebacondarwin]

This change to the test actually occurs in step-10. See angular/angular-phonecat@5f6c5df#diff-4
So it would make sense to update that step in the tutorial instead.
Do you think you could create a new PR with a change that matches the diff above?

[derrickmar]

Sure I'll go ahead and do that.