Add missing dependencies to install script

install.sh

@@ -1,6 +1,12 @@
 #!/bin/bash
 # Install the required dependencies for CHGenerator
 
+# Install magick to resize images
+brew install imagemagick
+
+# Install avif to create AVIF versions of images
+npm install avif -g
+
 # Install the Javascript minifier (required if `minifyJavaScript = True`)
 # https://github.com/mishoo/UglifyJS
 npm install uglify-js -g