Real-world units of measure

[alezzacreative]

i would love us to have this very quick way to change the units in the ruler (its common in adobe products) an inkscape dev added it just yesterday after alot of user requests.
https://user-images.githubusercontent.com/63913433/163684811-305787d7-88ce-4dc8-9410-42c14d19baa9.mp4
thank you

[Keavon]

This should be one of the document settings, which we'll need to make a menu for, to set the relationship between resolution and real-world units, as well as the default units to display. We should have a math-in-the-inputs-boxes system which does automatic unit conversions as well, so you can type any unit and it converts to dimensions then displays in the default display units.