Support group_labels in yml for dimensions

Line 99 in bb8f5b4

class Dbt2LookerDimension(BaseModel):

measures seem to have this but not dimensions. probably all/most properties in available in https://docs.lightdash.com/references/dimensions/ should be represented here -- is this something lightdash is willing to maintain or would you want a contribution? @TuringLovesDeathMetal / @owlas - i figure full support for lightdash properties that can map to looker should be, in order to maximize the value of this utility for enabling looker customers to uncouple themselves from looker.

i suppose it might go somewhere around here:

dbt2looker/dbt2looker/generator.py

Line 246 in bb8f5b4

'description': column.meta.dimension.description or column.description,

as like, if column.meta.dimension.group_label: etc