Update REST API.md

Author: makoni

Documentation/REST API.md

@@ -148,14 +148,41 @@ uploadcare.storeFiles(withUUIDs: uuids) { (response, error) in
 let query = GroupsListQuery()
     .limit(100)
     .ordering(.datetimeCreatedDESC)
-		
+
 uploadcare.listOfGroups(withQuery: query) { (list, error) in
     if let error = error {
         print(error)
         return
     }
     print(list ?? "")
 }
+
+// using GroupsList object:
+let groupsList = uploadcare.listOfGroups()
+
+groupsList.get(withQuery: query) { (list, error) in
+    if let error = error {
+        print(error)
+        return
+    }
+    print(list ?? "")
+}
+
+// get next page
+groupsList.nextPage { (list, error) in
+    if let error = error {
+        print(error)
+        return
+    }
+}		
+// get previous page
+groupsList.previousPage { (list, error) in			
+    if let error = error {
+        print(error)
+        return
+    }
+    print(list ?? "")
+}
 ```
 
 ### Group info ([API Reference](https://uploadcare.com/api-refs/rest-api/v0.6.0/#operation/groupInfo?utm_source=github&utm_medium=referral&utm_campaign=uploadcare-swift)) ###