clicking on the annotate button when the annotation creation widget is opened
starts the creation of a new annotation.
{{! template for the slice widget }}
<div class='Ldt-sliceWidget'>
{{! the whole bar }}
<div class='Ldt-sliceBackground'></div>
<div class='Ldt-sliceLeftHandle'></div>
{{! the zone which represents our slice }}
<div class='Ldt-sliceZone'></div>
<div class='Ldt-sliceRightHandle'></div>
</div>