m1 install issue

[joamatab]

When installing tidy3d-beta on M1 macOs there is an issue installing nlopt

To reproduce:

• install mamba
• run pip install tidy3d-beta

to fix

1. mamba install nlopt
2. pip install tidy3d-beta

ideas to fix this:

• provide a conda package for tidy3d
• make nlopt an optional dependency
• publish nlopt wheels to pypi with no architecture

[joamatab]

related to stevengj/nlopt#439

and

DanielBok/nlopt-python#13

[momchil-flex]

Thanks! I think we should make nlopt optional. This goes together with something we discussed with @tylerflex recently, which is not importing the plugins in the main tidy3d.__init__. nlopt is only used in the dispersive material fitter.