Logistic Distribution Support

[OAGr]

It would be great to be able to handle Logistic distributions. Metaculus uses logistic distributions; this may allow (in the future) for users to use WideDomain to make distributions, then export them to Metaculus. (they would need to be fitted to logistic distributions as well, but one thing at a time).

Scipy has the code for this, we'd need to redo it in javascript or reasonML
https://docs.scipy.org/doc/numpy-1.16.1/reference/generated/numpy.random.logistic.html
https://github.com/scipy/scipy/blob/v1.4.1/scipy/stats/_continuous_distns.py

[NunoSempere]

I'll take this.

[OAGr]

Sounds great, let me know if you have any questions here.