add link to Telugu translation, related to https://github.com/Kozea/Radicale/issues/1906

DOCUMENTATION.md

@@ -1,5 +1,9 @@
 # Documentation
 
+## Translations of this page
+
+* [Telugu](https://github.com/Kozea/Radicale/blob/master/docs/DOCUMENTATION.te.md) by [@gowtham1412-p](https://github.com/gowtham1412-p)
+
 ## Getting started
 
 #### About Radicale