[ADF-1549] Added doc files for remaining Activiti libraries (#2354)

docs/content.widget.md

@@ -0,0 +1,37 @@
+# Activiti Content Component
+
+The component shows the content preview.
+
+<!-- markdown-toc start - Don't edit this section.  npm run toc to generate it-->
+
+<!-- toc -->
+
+- [Basic Usage](#basic-usage)
+  * [Properties](#properties)
+  * [Events](#events)
+
+<!-- tocstop -->
+
+<!-- markdown-toc end -->
+
+## Basic Usage
+
+```html
+<adf-content
+    [contentId]="'1001'">
+</adf-content>
+```
+
+### Properties
+
+The recommended set of properties can be found in the following table:
+
+| Name | Type | Default | Description |
+| --- | --- | --- | --- |
+| contentId | string |  | The content id to show. |
+
+### Events
+
+| Name | Description |
+| --- | --- |
+| contentClick | Invoked when the content is clicked. |