fix: JsonInput usage of background-image: url('./img/jsoneditor-icons.svg');

[LeandroTorresSicilia]

To support Next JS and SSR we copy all jsoneditor CSS styles used in JsonInput component in the forms modules, then when copy this styles there is a usage of background-image: url('./img/jsoneditor-icons.svg'); that now does not work, it seems not to be loading right the image and the arrows to expand and contract json view are not showed