Add embed to docs capabilities (#23698)

docs/__capabilities.md

@@ -255,3 +255,7 @@ This is some inner content.
 </details>
 
   [1]: https://en.wikipedia.org/wiki/Eclipse_(software)
+
+## Embed
+
+[example embed](__capabilities_inc.md ':include')

docs/__capabilities_inc.md

@@ -0,0 +1 @@
+Lorem ipsum dolor sit amet.