Snippet: callouts with a coloured left bar instead of a box

For people who find the default callouts too heavy:

.callout {
  background: transparent;
  border: none;
  border-left: 3px solid rgb(var(--callout-color));
  border-radius: 0;
  padding-left: 1em;
}

Works in any theme that uses the standard callout variables.

Lovely. I might steal this for Driftwood's 'quiet' mode, with credit.

@juno go for it!