Update doc/code_and_data_management.md

Co-authored-by: Filippo Cerpelloni <filippo.cerpelloni@gmail.com>

Author: sid0309

doc/code_and_data_management.md

@@ -77,7 +77,8 @@ What to put there? Should not become a data dump so not just a new space where a
 
 ## Get organised
 
-## Code style guides
+### Code style guides
+
 
 matlab
 https://www.mathworks.com/matlabcentral/fileexchange/46056-matlab-style-guidelines-2-0