Updated Readme and fixed foldername

README.md

@@ -18,7 +18,7 @@ TDengine is an open-sourced big data platform under [GNU AGPL v3.0](http://www.g
 
 # Documentation
 For user manual, system design and architecture, engineering blogs, refer to [TDengine Documentation](https://www.taosdata.com/en/documentation/)
- for details.
+ for details. The documentation from our website can also be downloaded locally from *documentation/tdenginedocs-en* or *documentation/tdenginedocs-cn*.
 
 # Building
 At the moment, TDengine only supports building and running on Linux systems. You can choose to [install from packages](https://www.taosdata.com/en/getting-started/#Install-from-Package) or from the source code. This quick guide is for installation from the source only.