automate metadata validation

[aappling-usgs]

Let's write a selenium script that sends metadata through https://mrdata.usgs.gov/validation/.

(An alternative would be to send it through a locally-installed version of mp, but that command-line program is only available for Windows, so I think we can avoid installation headaches if we can figure out the web version. That said, Selenium does require docker, so it might be a wash...)

[jordansread]

Cool idea. I think the SB crew uses a pythod-based validator that is slightly different. Maybe?

Perhaps that is an alternative. Would be awesome to set up a GH action to do a checker on PR :)