Vignettes mw

[wolbersm]

Hi @gravesti and @miriampedrera9

I have completed my review of the Readme, vignettes, and /simulations/paper/Paper_Results_Analysis documents.
Please have a look and then merge what you like and rebuild the webpage.

Some comments:

• Advanced vignette:
  • I commented the text and example around custom contrasts. Unless I am mistaken, setting the contrast for x2 to Helmert did not change the one-hot encoding for trt:x2, i.e. it did not work as advertised.
  • I commented the text and example around prediction. I.e. it was not quite clear what was predicted (the linear predictor?) and why this is useful in the current context.
• Table format etc in Paper_Results_Analysis.Rmd is not fully aligned with the arxiv publication but I feel it is "good enough".