new vignette "Working with baggr results" (?)

[wwiecek]

For v0.8. Take forest plots, pp_check, various types of baggr comparison plots, plots specific to binary data and dump it into a gallery-like vignette

[wwiecek]

Maybe also a vignette that differentiates between ATE (current baggr vignette) and general overview of meta-analysis (without ATE interpretation).