adding test with numpy constants

[campospinto]

On my machine these lines trigger an error when run with python3.12

    import numpy as np
    from sympde.topology import AffineMapping

    dim   = 2
    alpha = np.pi/2
    c1    = 0.2
    c2    = 1.5

    F =  AffineMapping(
        name='F', dim=2, c1=c1, c2=c2,
        a11=np.cos(alpha), a12=-np.sin(alpha),
        a21=np.sin(alpha), a22=np.cos(alpha),
    )

[campospinto]

One solution seems to convert all the numpy constants to native python constants in sympde/topology/mapping.py