Allow newline after "one of"

[benjie]

Prettier adds newlines around bulleted lists, which for example means that the ExecutableDirectiveLocation production becomes:

ExecutableDirectiveLocation : one of

- `QUERY`
- `MUTATION`
- `SUBSCRIPTION`
- `FIELD`
- `FRAGMENT_DEFINITION`
- `FRAGMENT_SPREAD`
- `INLINE_FRAGMENT`
- `VARIABLE_DEFINITION`

This PR ensures that spec-md parses this as it is intended.

Relates to #31 (prettier support). Another PR incoming.

[benjie]

Trying to make this work for both condensed and non-condensed content. Will mark as ready for review when I've achieved it.

[benjie]

Sorted. You're probably going to want to rename NL_NO_BULLET 🤷