add numerical constants pi, e, Euler's gamma, and imaginary I

[denehoffman]

Addresses #6 and adds some other nice constants. For example, you should now be able to run the following without error:

import sympy
import sympy2jax
theta, phi = sympy.symbols("theta phi")
y22 = sympy.Ynm(2, 2, theta, phi).expand(func=True)
mod = sympy2jax.SymbolicModule(y22)
mod(theta=0.1, phi=0.2)
# returns Array(0.00354597+0.00149921j, dtype=complex64, weak_type=True), which is the correct result for this spherical harmonic function
mod.sympy()
# returns: -sqrt(30)*exp(2*I*phi)*cos(theta)**2/(8*sqrt(pi)) + sqrt(30) *exp(2*I*phi)/(8*sqrt(pi))

I've also written a unit test for these constants, although I had to use jnp.isclose rather than == I believe because of some type conversions. If someone knows how to make this nicer, please do so!

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[denehoffman]

The CI failure looks a little odd, I think that's unrelated. Let me see if I can fix that.

From a quick search, I believe changing isort 5.10.1 to a newer version might fix this (source)

see also: https://github.com/PyCQA/isort/releases/tag/5.11.5

[patrick-kidger]

Alright, try rebasing on top of the new main and I think the CI should be fixed. :)

[denehoffman]

@patrick-kidger nice (love the switch to ruff and pyproject.toml btw)! Okay, I've updated my PR with the changes you mentioned, let me know how it looks.

update: oops, not sure why the pre-commit didn't do the formatting but I've run black on it now so it should pass this time.

[patrick-kidger]

Marvellous! Just merged. I'll do a new release with this now.

[denehoffman]

Thank you!