Update documentation and workflow for adding icons

[karenmajewicz]

We used to have a separate repo for icons here: https://github.com/geoblacklight/geoblacklight-icons

This repo is not archived, but we have been adding icons as SVG directly to the GeoBlacklight repo itself. Our documentation still includes mention of the https://icomoon.io and using geoblacklight-icons.json

[ewlarson]

Reviewing this...

I still like IcoMoon and the geoblacklight-icons.json file. I'd vote to keep them in the application and our documentation. IcoMoon is very helpful for working with the SVG set as a whole.

We should archive the geoblacklight-icons repo. That hasn't been maintained for 5 years. I'll do that now.

[ewlarson]

GeoBlacklight Icons repo is now archived: https://github.com/geoblacklight/geoblacklight-icons

[ewlarson]

Moving to "Review" for further discussion

[ewlarson]

To add:

• [ ] Instructions for adding an icon to GBL proper (via PR)
• [ ] Better description of how an icon is rendered inside the application for testing