Update dataset card with additional metadata

Consistent README with dataset card

Add adhd2022 (6,774,224 rows)

Add adhd2010 (1,206,461 rows)

Update configs with all uploaded datasets

Fix configs: only include uploaded datasets, set valid default

Fix YAML indentation for dataset viewer

Add default config for dataset viewer

Add PGC Attention Deficit Hyperactivity Disorder GWAS summary statistics (parquet, 10k-row shards)

initial commit