Document all possible todo target types

doc/api/todos.md

@@ -27,7 +27,7 @@ Parameters:
 | `project_id` | integer | no | The ID of a project |
 | `group_id` | integer | no | The ID of a group |
 | `state` | string | no | The state of the to-do item. Can be either `pending` or `done` |
-| `type` | string | no | The type of to-do item. Can be either `Issue`, `MergeRequest`, `DesignManagement::Design` or `AlertManagement::Alert` |
+| `type` | string | no | The type of to-do item. Can be either `Issue`, `MergeRequest`, `Commit`, `Epic`, `DesignManagement::Design` or `AlertManagement::Alert` |
 
 ```shell
 curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/todos"