nicer vignette layout

Author: KatjaDanielzik

.Rbuildignore

@@ -4,3 +4,5 @@
 ^cran-comments\.md$
 ^revdep$
 ^\.github$
+^doc$
+^Meta$

.gitignore

@@ -13,3 +13,4 @@ doc/*
 Meta/*
 /doc/
 inst/doc
+/Meta/

vignettes/BayesVolcano.Rmd

@@ -20,7 +20,9 @@ knitr::opts_chunk$set(
 # Data requirements
 
 BayesVolcano requires as input:
-- posteriors of a Bayesian model fit stored in a data frame, where columns are parameters and rows are iterations. A wrapper function to extract the posterior exists for fits generated by [rstan](https://mc-stan.org/rstan) or [brms](https://paulbuerkner.com/brms) with the helper function extract_fit.R
+
+- posteriors of a Bayesian model fit stored in a data frame, where columns are parameters and rows are iterations. A wrapper function to extract the posterior exists for fits generated by [rstan](https://mc-stan.org/rstan) or [brms](https://paulbuerkner.com/brms) with the helper function extract_fit().
+The usage of extract_fit() requires installation of rstan or brms.
 
 ```{r setup}
 library(BayesVolcano)
@@ -96,7 +98,7 @@ the user.
 
 The simplest version is: 
 
-```{r}
+```{r,fig.width=7,fig.height=6}
 plot_volcano(results)
 ```
 
@@ -105,15 +107,15 @@ set threshold for pi is displayed as vertical black line and described in the
 subtitle.
 
 Titles and x-axis labels can be set with:
-```{r}
+```{r,fig.width=7,fig.height=6}
 plot_volcano(results, 
              title = "My amazing plot",
              xlab = "My informative parameter")
 ```
 
 
 To add the set CrI use:
-```{r}
+```{r,fig.width=7,fig.height=6}
 plot_volcano(results,
              CrI = TRUE)
 ```
@@ -124,7 +126,7 @@ to the subtitle.
 To color code the points the user can choose a character of numerical column
 from the annotation_df
 
-```{r}
+```{r,fig.width=7,fig.height=6}
 plot_volcano(results,
              CrI = FALSE,
              color = "group")
@@ -137,13 +139,13 @@ plot_volcano(results,
 To add labels the [ggrepel](https://cran.r-project.org/web/packages/ggrepel/vignettes/ggrepel.html)
 is employed:
 
-```{r}
+```{r,fig.width=7,fig.height=6}
 plot_volcano(results, label = "label")
 ```
 
 To only display labels above thresholds for the parameter value and pi set:
 
-```{r}
+```{r,fig.width=7,fig.height=6}
 plot_volcano(results, 
              label = "label",
              label.parameter.threshold = 1.5,
@@ -153,7 +155,7 @@ plot_volcano(results,
 Grey lines are added to visualize the threshold and a subtitle is added.
 
 Of course color and labels can be combined:
-```{r}
+```{r,fig.width=7,fig.height=6}
 plot_volcano(results, 
              color = "group",
              label = "label",