message: Add a printer case for TSExternalModuleReference.
diff: @@ -2065,6 +2065,9 @@ function genericPrintNoParens(path, options, print) {
  return concat(parts);
  + case "TSExternalModuleReference":
  + return concat(["require(", path.call(print, "expression"), ")"]);
  +
  case "TSModuleDeclaration":
  return concat([
  n.declare ? "declare " : "",
  