Feature Request - Preview Results / Query

Firstly.... Thank you for this tool!

It has saved countless hours of going back and forth to the GCP Console to validate columns, queries, run costs etc.

I was wondering if you would be able to update your 'Dataform Tools' feature slightly

If possible I would love to be able to set a 'sample' size as well as a custom 'limit' size. See Documentation [here](https://cloud.google.com/bigquery/docs/table-sampling#using_table_sampling)

In addition to this. Being able to see the columns and types of a given SQLX table definition would be awesome... using INFORMATION_SCHEMA.Columns like:

[Documentation](https://cloud.google.com/bigquery/docs/information-schema-columns)
```SQL
SELECT
column_name, data_type
FROM
``..INFORMATION_SCHEMA.COLUMNS
WHERE
table_name=""
```

I will attempt to write a PR for these later this week but I also just wanted to share my appreciation for your extension!

Cheers!