Restore `Leopard` and `Yosemite` support in v3

[lgarron]

This requires porting:

https://github.com/lgarron/folderify/blob/f86e013a7aadfe38a520b74a96d70552ecce3b88/folderify/__main__.py#L309-L387 https://github.com/lgarron/folderify/blob/f86e013a7aadfe38a520b74a96d70552ecce3b88/folderify/__main__.py#L469-L490

[lgarron]

I spent a few hours implementing this and concluded that it's not not worth the additional maintenance cost, especially given that:

• macOS Big Sur came out in 2020, meaning that few people would have reason to use older folder styles.
• The Python package still works, for anyone who would like the older icons.

To use an older style, run:

pip3 install folderify
python3 -m folderify --macOS 10.5 /path/to-icon.png

[lgarron]

I've documented how to use folderify v2 for this, at: https://github.com/lgarron/folderify#os-x-macos-10