Add information on exploring data exported from Google's BigQuery database

[ehumph]

There's a section that says these instructions are coming soon. I've added a link to the Terra instructions as a temporary measure, but it should be updated with AnVIL-specific documentation, perhaps. https://support.terra.bio/hc/en-us/articles/360036932671-How-to-retrieve-detailed-workflow-cost-information-on-GCP

[KatherineCox]

#154 was working on this but was never finished. It's >2 years old at this point, so, not sure how out-of-date it is, just mentioning it here in case it's useful if we decide to pick this back up.

[avahoffman]

Let's link to the terra docs. According to the larger team, this is going to be the strategy with portal going forward.