Update testflight.md

Author: ps2

fastlane/testflight.md

@@ -2,7 +2,7 @@
 
 These instructions allow you to build Loop without having access to a Mac. They also allow you to easily install Loop on phones that are not connected to your computer. So you can send builds and updates to those you care for easily, or have an easy to access backup if you run Loop for yourself. You do not need to worry about correct Xcode/Mac versions either. An app built using this method can easily be deployed to newer versions of iOS, as soon as they are available.
 
-The setup steps are somewhat involved, but nearly all are one time steps. Subsequent builds are trivial.
+The setup steps are somewhat involved, but nearly all are one time steps. Subsequent builds are trivial.  Note that TestFlight requires apple id accounts 13 years or older. Your app must be updated once every 90 days, but it's a simple click to make a new build and can be done from anywhere.
 
 ## Prerequisites