adding details pulldown to selected lessons

[mistrm82]

This is an HTML tag taht would be useful for "try it on your own" sections, where the code is hidden initially but clicking on it will make it available

```bash $ idr --samples Pou5f1-rep1_sorted_peaks.narrowPeak Pou5f1-rep2_sorted_peaks.narrowPeak \ --input-file-type narrowPeak \ --rank p.value \ --output-file Pou5f1-idr \ --plot \ --log-output-file pou5f1.idr.log ```

[rkhetani]

<details> <pre> <code> ## plot using ggplot2

ggplot(melted_top20_sigOE) + geom_point(aes(x = gene, y = normalized_counts, color = sampletype)) + scale_y_log10() + xlab("Genes") + ylab("Normalized Counts") + ggtitle("Top 20 Significant DE Genes") + theme_bw() + theme(axis.text.x = element_text(angle = 45, hjust = 1)) + theme(plot.title=element_text(hjust=0.5)) </code> </pre> </details>

[rkhetani]

The method listed above works nicely for html rendered markdown, looks a little funky without rendering.

[mistrm82]

Does anyone want to take a stab at this? It would be nice feature to have