add ListConverter

[ddxl123]

similar to:

TextColumn get list => list<String>()();

[simolus3]

I think there are to many uncertainties on how that list should be saved? As an encoded JSON array? I could see the argument for a builtin JSON column type if that's what you're interested in, but type converters are (I hope) fairly easy to write and to integrate into the database, so I'm not sure if there are that many that drift should provide out of the box.