Add note about countdown program

Author: mrseanryan

useful-scripts/readme.md

@@ -8,3 +8,11 @@ link files were created as follows: (so we can type X rather than X.sh)
 ln -s lstree.sh  lstree
 chmod +x lstree
 ```
+
+## note about the countdown program
+
+This is precompiled and downloaded from github.
+
+origin = https://github.com/antonmedv/countdown/releases
+
+