Add new link to Product External from PDS4 Documents page

[jordanpadams]

💡 Description

Related to CCB-357.

Refs https://github.com/NASA-PDS/pds4-information-model/issues/614

URLs:

• https://pds.nasa.gov/datastandards/documents/product_external_usage_guide.pdf
• https://pds.nasa.gov/datastandards/documents/product_external_usage_guide.docx

PDF/Word Doc: Product_External Usage Guide.docx (we won't link this online, but should have a copy of this somewhere) Product_External Usage Guide.pdf

• [x] Add bullet to bottom of the page that looks like this: Product External Usage Guide (link to PDF) Information on when and how to use Product_External, an extension to the PDS4 Information Model to allow for labeling and storage of products which are not suitable for being archived in the PDS.

NOTE: This is only supposed to be staged prior to release. If it is easier to just include this in the official release, that is fine too.

[c-suh]

@jordanpadams this is available to see on gamma and, if all looks well, will be put onto production with the other changes for the build release.

[c-suh]

This is available on gamma and will be released with the rest of the build documents updates.