Change to Floating numbers where it would make sense

[lucamug]

Most properties can be described only as Integer now because, for example

px : Int -> Length

but browser are actually behaving differently if given non-integer values because the density of screen is getting higher and higher.

This can create unwanted behaviour, especially if these small discrepancy are adding up.

This is an example of an animation that is not smooth as it could be because the height can only be expressed with integer numbers:

https://ellie-app.com/8z6hqHxjtnra1

[lucamug]

This is a better example: https://ellie-app.com/8z77CXZD425a1