message: create AtRoomPill when autocomplete returns
diff: @@ -95,8 +95,12 @@ export default class AutocompleteWrapperModel {
  const firstChr = completionId && completionId[0];
  switch (firstChr) {
  case "@": {
  + if (completionId === "@room") {
  + return this._partCreator.atRoomPill(completionId);
  + } else {
  return this._partCreator.userPill(text, completionId);
  }
  + }
  case "#":
  return this._partCreator.roomPill(completionId);
  // also used for emoji completion
  