add 'latest Stable Release' Link to Readme.md

README.md

 # Freifunk Dresden: ffdd-server (current version 1.0.1)
 Configures an Debian (8/9) or Ubuntu-Server LTS (16.04) as Freifunk-Dresden Server, that could be used as internet gateway an as basis to add further services.
 
+**[latest Stable Release](https://github.com/cremesk/ffdd-server/tree/T_RELEASE_latest)**
+
 **[see UPDATE News](https://github.com/cremesk/ffdd-server/blob/master/UPDATES.md)**
 
 **[see Documentation - German](https://wiki.freifunk-dresden.de/index.php/Server_Internes)**