R Markdown - 在html输出中更改字体大小和字体类型

I am using R Markdown in RStudio and the knit HTML option to create HTML output. However, the font used in the ouput for plain text blocks is rather small and I would like to change it to a differnt font and increase the font size. Can someone show an example how to set the output font - workable without a lot of knowledge in html?I am using R Markdown in RStudio and the knit H