supported: add Neptune object types (#213)

Author: larshp

src/user-guide/reference/supported.md

@@ -166,6 +166,7 @@ order: 20
 | `WEBI` | Virtual End Point                                            |                                                           **Yes** | No        |
 | `XINX` | Extension Index                                              |                                                           **Yes** | *Planned* |
 | `XSLT` | Transformation                                               |                                                           **Yes** | *Planned* |
+| `ZN**` | Neptune Artifact                                             | **Yes** [Via Extension](https://github.com/neptune-software/dxp-sap-edition-abapgit-extension)  | N/A |
 
 If additional object types are required please add a comment to [issue](https://github.com/abapGit/abapGit/issues/5912)