latex包"indentfirst“在R-markdown中不起作用

---
output:
  pdf_document:
    pandoc_args: ["+RTS", "-K512m", "-RTS", "--pdf-engine=xelatex"]
    keep_tex: true
    toc: true
    number_sections: true
    fig_caption: true
    latex_engine: xelatex
    includes:
      in_header: preamble.tex
  html_document:
    toc: true
    toc_float:
      collapsed: false
    code_folding: hide
    theme: united
    highlight: tango
    number_sections: true
    fig_caption: true
    css: styles.css
---

# Section 1

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum auctor, nunc sed efficitur aliquet, enim odio lacinia nisl, at lacinia mauris odio at nunc. Sed euismod, nunc sed efficitur aliquet, enim odio lacinia nisl, at lacinia mauris odio at nunc.

# Section 2

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum auctor, nunc sed efficitur aliquet, enim odio lacinia nisl, at lacinia mauris odio at nunc. Sed euismod, nunc sed efficitur aliquet, enim odio lacinia nisl, at lacinia mauris odio at nunc.