Track metadata for images

[jimtyhurst]

• We are required to credit the sources of some of our images and probably should do it for others too.
• In addition to any references that appear on the website itself, we should track the metadata independently of the display of those images.

Possible Solutions

1. Create a metadata folder in the source code that contains a images-metadata.csv file with:
   • Fields
     • File name as it appears in our images folder in the website source code.
     • URL to original source.
     • Date the URL was accessed.
     • Name of producer, if known.
     • Credit requirements, i.e. image sites like unsplash.com give instructions for how to give credit to the photographer.
   • Exclude the metadata folder from the build.
     • Maybe use gatsby-plugin-exclude, so that metadata does not appear in the build?
     • Or maybe Gatsby only looks within the src directory for builds anyway? So maybe having metadata as a sister directory to src is sufficient to keep it out of the build artifacts.