fix: make callout detection case-insensitive (closes #171)

Jacky Zhao

2022-08-05 5c76d8dad9d993010c4e57c6de4e90911a3cd11a

 assets/styles/_callouts.scss

@@ -82,6 +82,7 @@
  padding-bottom: 0.25em;
  color: var(--dark);
  background-color: var(--lightgray);
  border-left: 6px solid var(--primary) !important;
  & > p {
    border-top-right-radius: 5px;
    padding: 0.5em 1em;