zzzz-bs-sass.md
In bslib: Custom 'Bootstrap' 'Sass' Themes for 'shiny' and 'rmarkdown'

bootstrap-heading() mixin approximates %heading placeholder

Code
  heading_placeholder
Output
  [1] "%heading {"                               
  [2] "  margin-top: 0; // 1"                    
  [3] "  margin-bottom: $headings-margin-bottom;"
  [4] "  font-family: $headings-font-family;"    
  [5] "  font-style: $headings-font-style;"      
  [6] "  font-weight: $headings-font-weight;"    
  [7] "  line-height: $headings-line-height;"    
  [8] "  color: var(--#{$prefix}heading-color);" 
  [9] "}"