[Feature Request] Enum Support
You've already indirectly talked about enum support in
https://github.com/moigagoo/norm/issues/34#issuecomment-544385989

Enums feel like a rather important thing in nim to me, so I think it would great to support it out of the box.

Since Postgres has an enumtype it should be kinda straight forward.

Regarding your question how to handle enums in sqlite:
I have this in my project atm, which encodes enums as strings and parses them back using `std/strutils.parseEnum`

```nim
func dbType*(T: typedesc[enum]): string = "STRING"
func dbValue*(val: enum): DbValue = DbValue(kind: dvkString, s: $val)
func to*(dbVal: DbValue, T: typedesc[enum]): T = parseEnum[T](dbVal.s)
```

I imagine this could be rather costly for huge databases, so I don't know if it's a great solution.
However the benefit is, that the meaning of the value is preserved in the database.

The alternative would be to encode the enum as ints, obviously. Probably that is the better default choice.
The best way would be, to enable norm users to choose I guess.

Thanks for all the work put into norm. It's great!