Bring back warning that was accidentally removed

README.md

@@ -1,3 +1,7 @@
+**These policies are in active development and so might contain changes that do not work with current versions of Firefox.**
+
+**You should use the [officially released versions](https://github.com/mozilla/policy-templates/releases) if you are deploying changes.**
+
 Policies can be specified using the [Group Policy templates on Windows](https://github.com/mozilla/policy-templates/tree/master/windows), [Intune on Windows](https://support.mozilla.org/kb/managing-firefox-intune), [configuration profiles on macOS](https://github.com/mozilla/policy-templates/tree/master/mac), or by creating a file called `policies.json`. On Windows, create a directory called `distribution` where the EXE is located and place the file there. On Mac, the file goes into `Firefox.app/Contents/Resources/distribution`.  On Linux, the file goes into `firefox/distribution`, where `firefox` is the installation directory for firefox, which varies by distribution or you can specify system-wide policy by placing the file in `/etc/firefox/policies`.
 
 | Policy Name | Description