Add documentation for circle endpoints

content/en/entities/circle.md

@@ -0,0 +1,34 @@
+---
+title: Circle
+description: Represents a collection of some users that follow the authenticated user.
+menu:
+  docs:
+    parent: entities
+---
+
+## Example
+
+```javascript
+  {
+    "id": "12249",
+    "title": "Friends"
+  }
+```
+
+## Required attributes
+
+### `id` {#id}
+
+**Description:** The internal database ID of the circle.\
+**Type:** String \(cast from an integer, but not guaranteed to be a number\)\
+
+### `title` {#title}
+
+**Description:** The user-defined title of the circle.\
+**Type:** String\
+**Version history:**\
+2.1.0 - added
+
+## See also
+
+{{< page-ref page="methods/circles.md" >}}