easy way to add custom emblems without manual file/cli setup

[simply-zaki]

currently adding a custom emblem in nemo requires creating an icon, naming it with the emblem- prefix, placing it in ~/.icons/hicolor//emblems/, running gtk-update-icon-cache, and restarting nemo. this isn't accessible

requesting a built-in gui way to add a custom image as an emblem directly, an "add custom emblem" button in properties > emblems that lets you pick an image and handles resizing/placement/cache refresh automatically