quanteda tutorials website is created by Hugo based on the Learn theme. Since Hugo accepts only Markdown and HTML, we use blogdown to generate those files from Rmarkdown.
You can add new pages to the content folder, but note that the file extension must be .Rmarkdown not .rmd, because
blogdown converts .rmd to .html and .Rmarkdown to .markdown. After adding pages, you probably have to rebuild the website by clicking the 'Build Website' button in the build panel in R Studio.
If you have blogdown installed, you can execute blogdown::serve_site() in the console to check how your pages will look like. It will start a web server on your local machine so that you can preview the changes in your browser. HTML files are saved in the 'public' folder.
After editing the website locally, commit all the changes and push them to the master branch. Netlify will then detect the changes and update the file on the server for you within a minute or so.