support StaticArrays

[stevengj]

It would be nice if the various rand(...) functions supported returning an SMatrix, for example if ::Val{n} is passed instead of n::Integer.

This improves performance and reduces memory allocations in cases where lots of small matrices need to be sampled. e.g. see this example from discourse which generates lots of 2x2 and 4x4 Haar-distributed unitary matrices.