subregion names

[iamdonovan]

This would merge the following changes/updates:

• for each region, add list of subregion names as a drop-down note
• update text for RGI06, RGI08, and RGI09
• update text for RGI01, incorporating previous changes from F. Paul
• update text for RGI19, incorporating previous changes from F. Paul

[fmaussion]

This is fantastic - I briefly checked all changes and it looks very good to me. Will merge, build, and you can check again if everything is OK

[fmaussion]

OK I added the ref to Hannesdottir2020 and the website is now updated - can you check?

[iamdonovan]

I don't see the updated reference, but the other pages seem fine. I found one small thing I forgot to fix for RGI01 - will open a second PR now.