esa-numbering-header.css

.markdown {
  counter-reset: h2 0;
}
.markdown h2 {
  counter-increment: h2;
  counter-reset: h3 0;
}
.markdown h3 {
  counter-increment: h3;
  counter-reset: h4 0;
}
.markdown h4 {
  counter-increment: h4;
}
.markdown h2:before {
  content: counter(h2)". ";
}
.markdown h3:before {
  content: counter(h2)"." counter(h3)" ";
}
.markdown h4:before {
  content: counter(h2)"." counter(h3)"." counter(h4)" ";
}