Create Examples Documentation for `electricpy.acpiv`

[engineerjoe440]

Right now, the general solver electricpy.acpiv is a little lack-luster, and could really benefit from some examples to help inform users how it can be used to solve for the various quantities.

Should just be a matter of adding an Examples section to the acpiv docstring; for e.g.,

Examples
--------
>>> import electricpy as ep
>>> S = ep.acpiv(VLL=<something>, I=<something-else>)
>>> ep.cprint(S)
<quantity>
>>> VLL = ep.acpiv(S=<something>, I=<something-else>)
>>> ep.cprint(VLL)
<quantity>
>>> VLN = ep.acpiv(S=<something>, I=<something-else>)
>>> ep.cprint(VLN)
<quantity>