add screenshot on how to paste the readcitationfile

[avallecam]

Is your feature request related to a problem? Please describe.
This step is not clear on how it should look like:

research-compendium/episodes/readmefile.Rmd

Lines 166 to 172 in d2cf149

	- Then, paste this chunk with the `echo=FALSE` option in the `README.Rmd`:
	```r
	readCitationFile(file = "inst/CITATION")
	```

Describe the solution you'd like
To visualize how the step should look like in the README.Rmd file. This must show that is an R chunk:

> ```{r}
> readCitationFile(file = "inst/CITATION")
> ```

Additional context
The text could show a white background screenshot of this section: