Include e.g. why we have to pass a jitter to `LatentGP` (see [comment](https://github.com/JuliaGaussianProcesses/ApproximateGPs.jl/pull/59/files?authenticity_token=eenE3GK8QMpUTnVNnhDwFD7lQnVjmDHueNjES3WJdJUa3E0XLSz7mfYQqbZsDB2dg0qylnT8VXX069chAoaviQ%3D%3D&file-filters%5B%5D=.jl&file-filters%5B%5D=.toml#r715694354))
