message: refactor: remove unnecessary code
diff: import { Encoder, Decoder, ExtensionCodec } from "@msgpack/msgpack";
  -export function isBuffer(maybeBuf: unknown): maybeBuf is BufferSource {
  - if (maybeBuf instanceof ArrayBuffer || ArrayBuffer.isView(maybeBuf)) {
  - return true;
  - } else {
  - return false;
  - }
  -}
  -
  enum ExtensionTypes {
  // must be in range 0-127
  GENERIC_MAP = 1,
  