DESC not working in jsonb type
It works fine for me:

```python

class T(Model):
    data = BinaryJSONField()
    class Meta:
        database = db

db.drop_tables([T])
db.create_tables([T])
T.create(data={'k1': 'v1', 'k2': 'v2'})
T.create(data={'k1': 'v3', 'k2': 'v4'})
T.create(data={'k1': 'v5', 'k2': 'v6'})

query = T.select().order_by(T.data['k1'].desc())
for row in query:
    print(row.data['k1'])
# prints:
# v5
# v3
# v1
```
.desc() not working in jsob table,

```
class Player(BaseModel):
   user_id = IntegerField()
   ivent_stats = BinaryJSONField(default={"safe": 0,
                                          "bomb": 0,
                                          "robbery": 0})

players = await db.execute(Player.select(Player.user_id, Player.ivent_stats).order_by((Player.ivent_stats['robbery']).desc()))
```

I trying to get robbery value from more to less, but it olvays returning less to more, what i do wrong?(