You can customize the details output:
Manipulating the title style
readLines(
  'https://raw.githubusercontent.com/metrumresearchgroup/covrpage/master/_pkgdown.yml'
  )|>
  details::details(
    summary = 'yaml example',
    lang = 'yml'
    )
title: covrpage
development:
  mode: auto
template:
  params:
    bootswatch: flatly
navbar:
  type: inverse
  right:
    - icon: fa-github fa-lg
      href: https://github.com/yonicd/covrpage
  structure:
    left:  [home, reference, articleindex, news]
    right: [github, twitter]
  components:
    articles: ~
    articleindex:
      text: Articles
      href: articles/index.html
    twitter:
      icon: fa-lg fa-twitter
      href: http://twitter.com/yoniceedee
hexURL:
  https://github.com/yonicd/covrpage/blob/master/inst/logo/covrpageLogoSCREEN.png?raw=true
reference:
  - title: "Setup"
    contents:
      - has_concept("setup")
  - title: "Invoking"
    contents:
      - has_concept("invoke")
  - title: "Covrpage Trends"
    contents:
      - has_concept("log")
  - title: "Covrpage Utilities"
    contents:
      - has_concept("utility")
articles:
  - title: "Basics"
    contents:
      - get-started
      - how-to-read-covrpage-report
  - title: "Advanced"
    contents:
      - Continuous_Integration
      - snapshots
  - title: "The Output"
    contents: 
      - tests_and_coverage