Support for nlme

[florianhartig]

I actually can't remember why I never decided to support it - I guess because it's mainly a package for normal residuals, so I didn't think there is a need, but technically it would probably be possible, given

https://rdrr.io/cran/nlme/man/simulate.lme.html

I don't think there is a simulate gls but this may fall back to simulate.lm ... we can check