Add example showing how to pass a pointing table to update_pointing

[nabobalis]

In GitLab by @wtbarnes on Apr 30, 2021, 08:02

When updating the pointing for many images, it is best to query the pointing table from the JSOC once (using get_pointing_table) for the appropriate date range and then pass this table in to each call to update_pointing rather than repeatedly querying the JSOC. However, our examples do not make this clear. We need an additional example or an update to the existing one that shows explicitly how to do this.