Have option to set solid/bold page grid to 5 units instead of 4 to emulate millimeter paper

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Is your feature request related to a problem? Please describe. I'm always frustrated when I want to use draw.io to produce a scaled diagram. I switch on 1mm as grid size but the bold grid lines are a multiple of 4 for the thin ones. They do not align to the numbers of the rulers

Describe the solution you'd like I'd like to have an option to define how the bold grid is produced. E.g. have it every 5 small ones (resulting in 5 mm). If I zoom out and the grid would be to dense a strategy would be nice. E.g. show every 5mm a think and ever 1cm a bold. or every 1cm a thin and every 5cm a bold. The ruler seems to have a nice logic for the generating the numbers. Maybe follow this logic for the bold lines, too?