bump netpd to 2.2.1 and Pd to 0.51-2 (win) 0.51-3 (mac)

build_macos.sh

 #!/bin/bash
 
 app_name="netpd"
-app_version="2.2"
+app_version="2.2.1"
 app_bundle_name="${app_name}-${app_version}.app"
 package_version=$(date +%Y-%m-%d)
 
 # Pd
-pd_archive_file=~/Downloads/pd-0.51-0.unsigned.mac.tar.gz
+pd_archive_file=~/Downloads/pd-0.51-3.unsigned.mac.tar.gz
 
 # Libraries
 ext_urls=()