feat(widgets): feature intro, term cards, paid posts lists

Close more zibll produck/posts widget gaps: media-tab feature intro,
taxonomy term cards, and paid/credits content list with CSS.

assets/css/frontend/widgets.css

@@ -5,3 +5,4 @@
 @import url("widget-slider.css");
 @import url("widget-batch3.css");
 @import url("widget-batch3c.css");
+@import url("widget-batch3d.css");