Readme: actually there is another syntax to display no fields

The sib-core doc mentions that if you don't want to display the different fields of a resource, you have to write <sib-display fields />

This syntax does not work: https://codepen.io/daedalus418/pen/pMdVqB

In the example with bordered with orange, I use fields => all fields are displayed. In the example bordered with blue, I use fields=" " => no fields displayed. The space between the quotes in the last example is important. If there are none, all fields are displayed, while in 0.7 we wrote data-fields="" and it worked very well.