[Feature] Add survival function to core class

[galenseilis]

SimDist/src/simdist/core.py

Line 12 in 0321ecc

class Distribution(ABC):

[galenseilis]

Although the complement of the CDF is often the simplest way to calculate this, there may be cases where the survival function won't be calculated that directly. I recommend implementing it with raise NotImplementedError rather than assuming the CDF exists as a default.