Build a macOS bundle for Intel and ARM (#266)

* Build a macOS bundle for Intel and ARM

* Build icon.icns file in a script

* Add imagemagick

* Add macOS bundling to pre/tagged-release actions

scripts/makeicns.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+set -e
+
+usage() {
+    cat <<EOF
+$0: Make a macOS icns file from an SVG with ImageMagick and iconutil.
+usage: $0 [SVG [ICNS [ICONSET]]
+
+ARGUMENTS
+    SVG     The SVG file to convert
+            Defaults to ./lan-mouse-gtk/resources/de.feschber.LanMouse.svg
+    ICNS    The icns file to create
+            Defaults to ./target/icon.icns
+    ICONSET The iconset directory to create
+            Defaults to ./target/icon.iconset
+            This is just a temporary directory
+EOF
+}
+
+if [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
+    usage
+    exit 0
+fi
+
+svg="${1:-./lan-mouse-gtk/resources/de.feschber.LanMouse.svg}"
+icns="${2:-./target/icon.icns}"
+iconset="${3:-./target/icon.iconset}"
+
+set -u
+
+mkdir -p "$iconset"
+magick convert -background none -resize 1024x1024 "$svg" "$iconset"/icon_512x512@2x.png
+magick convert -background none -resize 512x512 "$svg" "$iconset"/icon_512x512.png
+magick convert -background none -resize 256x256 "$svg" "$iconset"/icon_256x256.png
+magick convert -background none -resize 128x128 "$svg" "$iconset"/icon_128x128.png
+magick convert -background none -resize 64x64 "$svg" "$iconset"/icon_32x32@2x.png
+magick convert -background none -resize 32x32 "$svg" "$iconset"/icon_32x32.png
+magick convert -background none -resize 16x16 "$svg" "$iconset"/icon_16x16.png
+cp "$iconset"/icon_512x512.png "$iconset"/icon_256x256@2x.png
+cp "$iconset"/icon_256x256.png "$iconset"/icon_128x128@2x.png
+cp "$iconset"/icon_32x32.png "$iconset"/icon_16x16@2x.png
+iconutil -c icns "$iconset" -o "$icns"