Documentation support for enums
It's probably a good idea to add documentation support for top-level enums. One of the approaches suggested by @julie-bsx is:

```yaml
enums:
  animals:
    doc: |
      Animals you might find at the office.
    1: dogs
    2: cats
    3: birds
    4: programmers
```

Original discussion was in https://github.com/kaitai-io/kaitai_struct/issues/356