Rendering bookdown doesn't show inline figures and images

Question

I am trying to create a GitBook with bookdown. You can see it here: https://swvanderlaan.github.io/A_Practical_Primer_in_Human_Complex_Genetics/.

You can also see that basically all the images are missing. Yet, they are really made and/or on the repository. The strange is, that when I render the book it does show all the images in the RStudio Preview window; they're just not shown online.

Below is my index.Rmd file.

--- 
title: "A Practical Primer in Human Complex Genetics"
subtitle: "with a use-case in cardiovascular disease"
author: "[dr. Sander W. van der Laan](https://vanderlaanand.science) [![](./img/_logo/twitter_circle_blue.png){width=2%}](https://www.twitter.com/swvanderlaan) [![](./img/_logo/email_circle_blue.png){width=2%}](mailto:[email protected])"
date: "Version 2.0.2 (`r Sys.Date()`)"
description: "This is a practical primer in human complex genetics with a use-case in cardiovascular disease. The output format for this primer is bookdown::gitbook."
documentclass: book
github-repo: swvanderlaan/A_Practical_Primer_in_Human_Complex_Genetics
link-citations: yes
bibliography:
- bibliography/book.bib
- bibliography/packages.bib
biblio-style: apalike
site: bookdown::bookdown_site
always_allow_html: true
#cover-image: "images/cover.png"
#apple-touch-icon: "touch-icon.png"
#apple-touch-icon-size: 120
#favicon: "favicon.ico"
---

# About this primer
![](img/_headers/banner_man_standing_dna.png){width=100%}
\```{r include = FALSE}
if(!knitr:::is_html_output())
{
  options("width"=56)
  knitr::opts_chunk$set(tidy.opts=list(width.cutoff=56, indent = 2), tidy = TRUE)
  knitr::opts_chunk$set(fig.pos = 'H')
}
\```

[a slab oftest is here]

**Ready to start?**

Your first point of action is to prepare your system for this course in Chapter \@ref(somebackgroundreading).

To be clear, those \ in the code near {r include = FALSE} and at the end of that code block aren't there in the original code.

How can I fix this?