text: Title: Document SQL runtime parameters
  Body: We recently added a new feature to allow runtime SQL parameters. This lets users read products from upstream tasks, compute some parameters, and use these parameters to render the SQL script. However, this feature hasn't been documented.
  
  For context, see #466
  
  For a code example, see: https://github.com/ploomber/ploomber/blob/84d836fa5a5f2368fe96db4a9181b5b2d6687d2b/tests/tasks/test_tasks_sql.py#L189