add `DataAPI` metadata methods
From Bogumil:
Could you please add to the release plan of Parque2.jl support for https://github.com/JuliaData/DataAPI.jl/pull/48 for the created Parquet tables. Only read methods need to be implemented for Parquet tables:
DataAPI.metadataDataAPI.metadatakeysDataAPI.colmetadataDataAPI.colmetadatakeys