add documentation archive url

Author: sagorbrur

README.md

@@ -62,7 +62,7 @@ print(tokens)
 ## Documentation
 Full documentation are available [here](https://github.com/sagorbrur/bnlp/tree/master/docs)
 
-If you are using previous version of **bnlp** check the documentation [archive]()
+If you are using previous version of **bnlp** check the documentation [archive](https://github.com/sagorbrur/bnlp/tree/master/docs/archive)
 
 ## Contributor Guide