Add Gauss random function

### The Problem

Currently it is not simple to create using a gauss/normal distribution. It is one of the most commonly found naturally occurring distributions.

### A Solution

create a gauss() function. It should take mean and standard deviation parameters.

### Alternatives

It is possible to manually implement the distribution into an expression. If you add 12 random() outputs together and then subtract that from 6, the result will be a close approximation to a gauss distribution.

For example, generating a patch of path blocks that decay radially using this implementation:
`//g dirt_path a=0; for(b=0;b<12;b++){a+=random();} (6-a)^2>(x*2)^2+(z*2)^2`

But it would be much simpler and faster to be able to write `//g dirt_path gauss(0,1)>(x*2)^2+(z*2)^2`

### Anything Else?

_No response_