Provide native icon.icns for macOS

.gitignore

@@ -12,6 +12,7 @@ coverage/
 dist/
 node_modules/
 out/
+icon.iconset/
 
 .yalc/
 

freelens/build/icon.sh

@@ -1,14 +1,30 @@
 #!/bin/bash
 
+set -euo pipefail
+
 ## macOS
-magick -background none icon.svg -density 300 -resize 408x408 -bordercolor transparent -border 52 -verbose icon.png
+rm -rf icon.iconset
+mkdir icon.iconset
+for i in 16 32 64 128 256 512 1024; do
+	border=$(("${i}000" * 100 / 1000000))
+	size=$((i - 2 * border))
+	half=$((i / 2))
+	if [[ $i -ne 1024 ]]; then
+		magick -background none icon.svg -density 400 -resize "${size}x${size}" -bordercolor transparent -border "${border}" -verbose "icon.iconset/icon_${i}x${i}.png"
+	fi
+	if [[ $i -ne 16 ]]; then
+		magick -background none icon.svg -density 400 -resize "${size}x${size}" -bordercolor transparent -border "${border}" -verbose "icon.iconset/icon_${half}x${half}@2x.png"
+	fi
+done
+iconutil --convert icns -o icon.icns icon.iconset
+rm -rf icon.iconset
 
 ## Windows
-magick -background none icon.svg -define icon:auto-resize=256,16,20,24,32,40,48,60,64,72,80,96 -verbose icon.ico
+magick -background none icon.svg -density 400 -define icon:auto-resize=256,16,20,24,32,40,48,60,64,72,80,96 -verbose icon.ico
 
 ## Linux
 for i in 16 22 24 32 36 48 64 72 96 128 192 256 512; do
 	border=$(("${i}000" * 38 / 1000000))
 	size=$((i - 2 * border))
-	magick -background none icon.svg -density 300 -resize "${size}x${size}" -bordercolor transparent -border "${border}" -verbose "icons/${i}x${i}.png"
+	magick -background none icon.svg -density 400 -resize "${size}x${size}" -bordercolor transparent -border "${border}" -verbose "icons/${i}x${i}.png"
 done