feat(core): add gauss function to Random

[ajs1998]

gauss(mean, stdev) will return a normally distributed random value with a given mean and stdev.

The implementation was ported to TypeScript from Python's random.gauss(): https://docs.python.org/3/library/random.html#random.gauss

It includes a small optimization that caches a second independent random value
since the function always generates a pair.

Closes #704

[ajs1998]

For reference, this is Python's implementation:

def gauss(self, mu=0.0, sigma=1.0):
  random = self.random
  z = self.gauss_next
  self.gauss_next = None
  if z is None:
      x2pi = random() * TWOPI
      g2rad = _sqrt(-2.0 * _log(1.0 - random()))
      z = _cos(x2pi) * g2rad
      self.gauss_next = _sin(x2pi) * g2rad

  return mu + z * sigma

[ajs1998]

The left is uniform distribution between 0-200

The right is gaussian distribution with a mean of 150 and standard deviation of 10

Here's another where the right has a mean of 150 and standard deviation of 50

I'm not experienced enough with Motion Canvas to make a histogram. I could probably do it though if you need further convincing that this works. Just eyeballing it I can see how the distribution isn't uniformly random, and my changes to the standard deviation match what I expect.

I also confirmed that the random values are reproducible just like the other methods in Random. Makes sense because I'm just using this.next() for random values.