NO in yaml frontmatter is handled as no, which is false

[Ezian]

Reproduce

---
terrain:
    type: grassland
    mixed:
        - type: lake
          sides:
            - NO
---

In this case, script will fails and the map won't be generated

How to fix it

Retained solution is to use english cardinal direction (West instead of Ouest). NO will be no more an issue.

But in order to don't require a major update (it's kind of early to update the major version), we shouldn't introduce breaking changes. So Old way to write cardinal should be accepted, but deprecated (generate an error message, but handle it).