smashingboxes/cardboard

.c-markdown-editor {
  display: grid;
  grid-template-areas:
    "label ."
    "editor preview";
  grid-template-columns: 1fr 1fr;
  grid-column-gap: 10px;
}
.c-markdown-editor__label {
  grid-area: label;
}
.c-markdown-editor__input {
  grid-area: editor;
  vertical-align: top;
}
.c-markdown-editor__preview {
  grid-area: preview;
  vertical-align: top;
  word-wrap: break-word;
}