Distributions to add

[ben18785]

Univariate continuous:

• [ ] Ordered logistic
• [ ] Skew normal
• [ ] Exponentially-modified normal distribution
• [ ] Double exponential
• [ ] Logistic
• [ ] Gumbel
• [ ] Chi-square
• [ ] Weibull
• [ ] Frechet
• [ ] Rayleigh
• [ ] Wiener
• [ ] Pareto
• [ ] Pareto type 2

Univariate discrete:

• [ ] Hypergeometric
• [ ] Categorical
• [x] Uniform

Multivariate:

• [ ] Matrix normal (perhaps show covariance matrix structure somehow)
• [ ] Von Mises
• [ ] Wrapped Cauchy
• [ ] Normal-inverse-gamma
• [ ] Dirichlet-multinomial
• [ ] multivariate logistic (/logit?) normal (more flexible version of Dirichlet)

[ben18785]

Also, change categorisations to match those of Stan as otherwise the lists will be too long.