Function isCompass

isCompass(c: string): c is values
Type guard to check if a string is a valid Compass direction
Parameters
- c: string
  String to check
Returns c is values
True if the string is a valid Compass direction
Example
```
isCompass('n') // true
isCompass('northeast') // false
isCompass('invalid') // false
```
- Defined in models.ts:798