Show Real-time measures of km/h and month-length

[Leartin]

I had a question on Discord:

if a vehicle costs $0.1 /km, and it goes 40km/h i dont see the total costs of that vehicle increase by $4 every hour, its way slower than that

Why that calculation doesn't work is easy enough to explain, but I think the user has a point: I don't think the game shows the required information to make the correct calculations anywhere. The only place I know of is in factories, giving a production rate in real-life minutes.

I think we should show two more measures somewhere to aid players who prefer Excel over Experimentation:

A) How long a month is in real-life-minutes (possibly in the settings near the bits_per_month setting)
B) What km/h means in terms of tiles/minute, both directions (1 km/h = x tiles/minute, 1 tile/minute = x km/h) - Just showing the factor somewhere should be enough, I don't think adding the info to each vehicle is beneficial (breaks immersion and the depot is way too cluttered anyway)