clicking on the annotate button when the annotation creation widget is opened
starts the creation of a new annotation.
{{! template for the slider widget - it's composed of two divs we one overlayed on top
of the other }}
<div class='Ldt-sliderBackground'></div>
<div class='Ldt-sliderForeground'></div>
<div class='Ldt-sliderPositionMarker'></div>