Updated agi documentation on appdata library

AGI Documentation.md

@@ -468,6 +468,21 @@ To use the user default option which user has set in File Manager WebApp, pass i
 filelib.aglob("user:/Desktop/*.jpg", "user");
 ```
 
+### appdata
+
+An API for access files inside the web folder. This API only provide read only functions. Include the appdata lib as follows.
+
+```
+requirelib("appdata");
+```
+
+#### appdata functions
+
+```
+appdata.readFile("UnitTest/appdata.txt"); //Return false (boolean) if read failed
+appdata.listDir("UnitTest/backend/"); //Return a list of files in JSON string
+```
+
 
 
 ### imagelib