Add Open-Source Emoji Collections

[danielvartan]

Some users have requested emoji support in the NetLogo repository (see NetLogo/NetLogo#2354 and NetLogo/NetLogo#2354). Until NetLogo provides native SVG support, we can transform existing open-source emoji collections into compatible turtle shape files.

The following projects offer suitable assets for conversion:

• OpenMoji
• Twemoji
• Blobmoji
• Noto