add dynamic date range calculation for dates, and add color gradient component, add color gradient for language and chrono
<div>{{ color-gradient domainStart=minCount domainEnd=maxCount scale=colorScale }}</div>
{{#each decades as |decade| }}
<div class="interval">
{{input type="checkbox" checked=(is-checked date decade) indeterminate=(is-indeterminate date decade) click=(action 'selectDecade' decade)}}
<ul class="{{ decade }}">
{{#each (range decade 10) as |year| }}
{{ visu-chrono-year datestats=datestats year=year range=rangeArray scale=colorScale }}
{{/each}}
</ul>
</div>
{{/each}}