feat(components): add icon-picker component

[patdec]

This component is not completed: It remains to deal with the url of css file: see app/javascript/editor/components/kit/icon-picker.vue l63:

@import url('http://localhost:3000/fonts/fonts.css');

Below, I pasted the content of my section yml file related to the component:

  - label: "Icônes"
    id: icon
    type: icon
#    prefix: 'fa'
    default: 'icon-af-certif'
    presets: ['icon-af-certif','icon-af-counter','icon-af-map','icon-af-headphone']

We can see a line prefix: 'fa'. I added this option to take account of some libraries requirements as FontAwesome.

I have dropped css and fonts files in /public/fonts directory of main Rails application:

[did]

already implemented