If you want to add R Markdown html pages (or any other html content), just do this:
open the R Markdown generated html file in a text editor
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copy everything to the clipboard
open a new dokuwiki page, define a headline as usual and paste the text from the html file below the headline
Please note that you should not define a title, author or date in the R Markdown document but define it as headline inside teachwiki (e.g. below the default template). To match the headers of the rest of your teachwiki, using “#####” for first level headlines in the R Markdown file is a good choice.