[pyspark][doc] add more doc for pyspark (#8271)
[pyspark][doc] add more doc for pyspark (#8271)


Co-authored-by: fis <e16b25b7883ebdfb0cca6b409cf5afe1de1589fd@outlook.com>
dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost