message: Always store sent MD messages as MD in history
  Because converting them to HTML when they got sent as HTML seems a bit pointless when they're just going to get transformed back again when retrieved from history.
  Fixes regression
diff: @@ -556,9 +556,15 @@ export default class MessageComposerInput extends React.Component {
  sendTextFn = this.client.sendEmoteMessage;
  }
  + if (this.state.isRichtextEnabled) {
  this.historyManager.addItem(
  contentHTML ? contentHTML : contentText,
  - contentHTML ? 'html' : 'markdown');
  + contentHTML ? 'html' : 'markdown',
  + );
  + } else {
  + // Always store MD input as input history
  + this.historyManager.addItem(contentText, 'markdown');
  + }
  let sendMessagePromise;
  if (contentHTML) {
  