Add emmeans to bibtex file

[ddsjoberg]

@Manual{emmeans,
  title = {emmeans: Estimated Marginal Means, aka Least-Squares Means},
  author = {Russell V. Lenth},
  year = {2022},
  note = {R package version 1.7.5},
  url = {https://github.com/rvlenth/emmeans},
}

[ddsjoberg]

Also add gtreg and ggsurvfit

@Manual{gtreg,
  title = {gtreg: Regulatory Tables for Clinical Research},
  author = {Shannon Pileggi and Daniel D. Sjoberg},
  year = {2022},
  note = {https://github.com/shannonpileggi/gtreg,
https://shannonpileggi.github.io/gtreg/},
}

@Manual{ggsurvfit,
  title = {ggsurvfit: Easy and Flexible Time-to-Event Figures},
  author = {Daniel D. Sjoberg and Mark Baillie},
  year = {2022},
  note = {R package version 0.1.0},
  url = {https://CRAN.R-project.org/package=ggsurvfit},
}