Update generate_favicon in Makefile

Co-authored-by: Lars Göttgens <lars.goettgens@gmail.com>

Makefile

@@ -7,10 +7,6 @@ generate_badge:
 	curl -o "badge.svg" "https://img.shields.io/badge/tested_with-Aqua.jl-05C3DD.svg?logo=data:image/svg+xml;base64,$$SVG_BASE64"
 
 generate_favicon:
-	convert -background none docs/src/assets/logo.svg -resize 256x256 logo.png
-	convert logo.png -gravity center -background none -extent 256x256 logo256.png
-	convert logo256.png -resize 16x16 logo16.png
-	convert logo256.png -resize 32x32 logo32.png
-	convert logo256.png -resize 48x48 logo48.png
-	convert logo16.png logo32.png logo48.png logo256.png docs/src/assets/favicon.ico
-	rm logo.png logo256.png logo16.png logo32.png logo48.png
+	convert -background none docs/src/assets/logo.svg -resize 256x256 -gravity center -extent 256x256 logo.png
+	convert logo.png -define icon:auto-resize=256,64,48,32,16 docs/src/assets/favicon.ico
+	rm logo.png