Squircle and rounded cube openScad modules

Modules for OpenScad that draw a parallelepiped with rounded edges. In other words, these are analogs of the OpenScad "cube" function, only with rounding. Two modules are presented:

• The usual "roundedCube", which rounds the corners of the rectangle lying at the base of the parallelepiped using circles.
• The more modern "squircleCube", where a "squircle" is used instead of a rectangle at the base of the parallelepiped.

A "squircle" is a special shape, which produced by curve that follows the equation

$$ \left| \frac{x}{a} \right|^n+\left| \frac{y}{b} \right|^n=1 $$

Where a is the length along the X axis, b is the length along the Y axis, n is the parameter responsible for the power of rounding. More details about the squircle shape can be found in Wikipedia.
In short, the use of such curves gives a smoother rounding of the corners of the rectangle without sharp transitions. And it is convenient to adjust the power of rounding by changing the parameter n. Then greater the n - then less the power of rounding. For example, for n = 2 - there will be an ellipse.