Adding an Icon to a Setting Name

To add an icon to a setting name without causing crashes,

• Make sure the icon file name does not contain hyphens
• Write @ICONFILENAME.svg setting name on addon.json
• Add ICONFILENAME.svg at /images/icons/ if missing
• Edit /background/load-addon-manifests.js to add iconfilenameIcon: "@ICONFILENAME.svg",
• Edit /addons/scratch-notifier/notifier.js for Scratch Notifier settings