build(dgeni): render class descriptions as markdown (#8153)

Author: willshowell

tools/dgeni/templates/class.template.html

@@ -10,7 +10,7 @@ <h4 id="{$ class.name $}" class="docs-header-link docs-api-h4 docs-api-class-nam
 </h4>
 
 {%- if class.description -%}
-<p class="docs-api-class-description">{$ class.description | safe $}</p>
+<p class="docs-api-class-description">{$ class.description | marked | safe $}</p>
 {%- endif -%}
 
 {%- if class.directiveSelectors -%}