I've created a link menu and I want to add a SVG icon before it.

This is my YML : 

```
double_vue_klesia.listeSwitch2:
  title: 'Double vue Klesia'
  route_name: double_vue_klesia.listeSwitch
  menu_name: navigation-principale
  weight: 4
  options:
    attributes:
      class:
        - listeSwitchMenuItem

```

I though adding a class and in CSS, adding the svg content would do the trick, but clearly it doesn't because it's breaking menu CSS.

This is my css : 

```
.listeSwitchMenuItem::before{
  content: url(../images/active.svg);
}

```

Is there another way more clean to do this through YML directly ?