chore(icons): add instructions on how to add icons

src/Utils/Icon.hs

@@ -29,6 +29,13 @@ type WidgetSiteless = forall site. WidgetFor site ()
 -- We collect all used icons here for an overview.
 -- For consistency, some conditional icons are also provided, having suffix True/False
 
+{- How to add icons:
+  - edit utils/rename-fa.json by adding "our-name": "fa-name"
+  - make sure to only use fontawesome v6.6.0 free icons
+  - delete directory node_modules
+-}
+
+
 ---------------------------------------------------------------------------
 -- IMPORTANT: Alert-Icons must be registered in alert-icons.js as well!!!
 ---------------------------------------------------------------------------