.o-main-container {
  margin: 2.25rem auto;
  max-width: 70ch;
  padding: 0 .5rem;
}

.o-main-container {
  margin: 2.25rem auto;
  max-width: 72em;
  padding: 0 .5rem;
}

Increase site width to 72em
GH-12: Increase site width to 72em
