Added macOS Big Sur support

Necessary to support the latest macOS release.

README.adoc

@@ -46,7 +46,7 @@ image::https://www.alchemists.io/images/screencasts/mac_os/cover.svg[Screencast,
 
 == Requirements
 
-. link:https://www.apple.com/macos/catalina[macOS]
+. link:https://www.apple.com/macos/big-sur[macOS Big Sur]
 . link:https://developer.apple.com/xcode[Xcode]
 
 == Setup

lib/settings.sh

@@ -5,7 +5,7 @@ set -o errexit
 set -o pipefail
 IFS=$'\n\t'
 
-export MAC_OS_BOOT_DISK_CREATOR="/Applications/Install macOS Catalina.app/Contents/Resources/createinstallmedia"
+export MAC_OS_BOOT_DISK_CREATOR="/Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia"
 export MAC_OS_BOOT_DISK_PATH="/Volumes/Untitled"
 export MAC_OS_WORK_PATH=/tmp/downloads
 export MAC_OS_CONFIG_PATH="../mac_os-config"