Add guidelines for documentation

documentation/docs/developer_guide/contribution_flowchart.md

@@ -6,6 +6,8 @@
 
 These guidelines are written from the perspective of a new contributor to CABLE wanting to start their first development. Notes are added when guidelines for subsequent contributions differ.
 
+:material-sim-alert: The CABLE documentation is an integral part of the CABLE code and its repository. The present guidelines apply for changes to the scientific code as well as to the documentation. All changes to the scientific code **must** be accompanied by adequate changes to the documentation. The changes to the documentation are expected to be part of the same set of changes as the scientific modifications. The documentation changes **must** not be submitted separately, except for corrections. You can refer to [the documentation guidelines][doc-guidelines] to know what level of documentation is expected and how to document code changes.
+
 !!! info "Resources"
 
     Please refer to [this cheat sheet page][cheatsheet] for quick references to Git, Markdown and FORD syntax.