message: allow optional commas for migration macro
diff: @@ -20,7 +20,7 @@ use schemamama_postgres::{PostgresAdapter, PostgresMigration};
  /// "DROP TABLE test;");
  /// ```
  macro_rules! migration {
  - ($version:expr, $description:expr, $up:expr, $down:expr) => {{
  + ($version:expr, $description:expr, $up:expr, $down:expr $(,)?) => {{
  struct Amigration;
  impl Migration for Amigration {
  fn version(&self) -> Version {
  