[FEATURE]:custom (narrower) type for a table

### Feature hasn't been suggested before.

- [x] I have verified this feature I'm about to request hasn't been suggested before.

### Describe the enhancement you want to request

I have a table like this :
```ts
const someTable = pgTable({
id:uuid().notNull().primaryKey(),
userId:uuid(),
categoryId:uuid(),
})
```
it should contain on and only one of userId and categoryId based on the business logic,
we can make the code work ( and type safe by putting checks everywhere or ( using ! operator for typescript in order to guarantee the value is there ) but that's not ideal.

something like this would solve the issue :
```ts
const someTable = pgTable<{id:string} &({userId:string} | {categoryId:string})>({
id:uuid().notNull().primaryKey(),
userId:uuid(),
categoryId:uuid(),
})
```
this could also be useful for different applications as well ( for example narrowing type of one column based on another column's type )

it is possible to pass a type for both select and insert if necessary but the idea of being able to narrow down the type is useful IMO.