Add link to official VR module forum thread

untill we have a proper wiki doc from VR module author @jseinturier.

src/docs/asciidoc/jme3/virtualreality.adoc

@@ -6,6 +6,8 @@
 :imagesdir: ..
 ifdef::env-github,env-browser[:outfilesuffix: .adoc]
 
+Please see this link:https://hub.jmonkeyengine.org/t/official-vr-module/37830/67[forum post] for additional information on JME Official VR module.
+
 jMonkeyEngine 3 has a wide range of support for Virtual Reality (VR). The known supported systems are:
 
 HTC Vive and systems supporting SteamVR/OpenVR