ENH: Support complex exponents; with i and/or a complex() function

Test equations for geogebra:

    equation -- what I think it looks like
    xi^2 -- Integer coordinate grid
    e^xπi -- Unit circle with another little circle also about the origin (0,0)
    e^(πi^x) -- crash / not responding: a(x)=e^(πi^(x))
                though it seems to work with x in Z+

    e^(x π i^π) -- somewhat scale-invariant interposed spirals around a single point attractor. (Zoom in/out)

Only SageMath preprocesses Python to replace XOR (^) with exp() or **, so:

  f(x) = x^2
  g(x) = x**2  # Python
  h(x) = exp(x, 2)
  x**2         # SymPy Gamma, Beta

Sympy Gamma: https://gamma.sympy.org/

Sympy Beta is SymPy Gamma compiled to WASM: https://github.com/eagleoflqj/sympy_beta