Added Beta SDK ToS to README; added link to Iterable's iOS SDK release notes

Author: Brad Umbaugh

README.md

@@ -530,9 +530,24 @@ To do this, Iterable sends a silent push notification some time (currently, 12 h
 
 For more information, take a look at:
 
+- Iterable's [iOS SDK Release Notes](https://support.iterable.com/hc/articles/360027798391)
 - Iterable's [Setting Up iOS Push Notifications](https://support.iterable.com/hc/articles/115000315806-Setting-Up-iOS-Push-Notifications) guide
 - Iterable's [Push Notification Setup FAQs](http://support.iterable.com/hc/articles/206791196-Push-Notification-Setup-FAQ-s)
 
+## Beta SDK terms of service
+
+Beta versions of Iterable’s iOS and Android SDKs should be used only for
+internal testing in a sandbox environment. Beta SDKs should not be used in
+production. Iterable may change, fix bugs or vulnerabilities in, remove
+features from, add features to, or otherwise improve or modify beta SDKs
+before removing their beta designation. Beta SDKs are provided "as is," and
+Iterable does not guarantee their functionality or provide support for their
+use in production.
+
+Iterable attempts to move beta SDKs out of beta (to general availability)
+four weeks after the start of the beta period. However, this timeline is not
+guaranteed
+
 ## License
 
 The MIT License