`SVG.PolarEquation` should draw a path using a polar equation

[StartAutomating]

The polar equation and its inputs should be embedded in a data attribute, as PowerShell.

(this will only require minor renaming to turn into JavaScript, since the [Math] classes are roughly the same).

Having this around simplifies the implementation of any complex shape that can be represented as a polar equation, such as:

• [ ] #238