Decorator to make properties symmetric

e.g. instead of:

```python
    _symmetric_builtins_ = ['uri']

    @property
    def uri(self) -> str:
        return f'mapbox://styles/mapbox/{self.value}-v{self.version}'
```

just:

```python
    @symmetric
    @property
    def uri(self) -> str:
        return f'mapbox://styles/mapbox/{self.value}-v{self.version}'
```
