Update documentation and typescript-definitions.

This is also associated with https://github.com/josteink/gmail.js/issues/4.

Author: josteink

README.md

@@ -663,6 +663,14 @@ Although hand picked, this method returns the checks on beta features and deploy
 
 Returns the Gmail localization, e.g. 'US'.
 
+#### gmail.check.is_new_data_layer()
+
+Returns `True` if the user is running Gmail with the new 2018 data-layer `False` otherwise
+
+#### gmail.check.is_new_gui()
+
+Returns `True` if the user is running Gmail with the new 2018 GUI `False` otherwise
+
 #### gmail.check.is_thread()
 
 Returns `True` if the conversation is threaded `False` otherwise

src/gmail.d.ts

@@ -281,6 +281,14 @@ interface GmailGet {
 ////////////////////////////////////////////////////////////////////////////////
 
 interface GmailCheck {
+    /**
+       Returns True if the user is running Gmail with the new 2018 data-layer
+     */
+    is_new_data_layer(): boolean;
+    /**
+       Returns True if the user is running Gmail with the new 2018 GUI
+     */
+    is_new_gui(): boolean;
     /**
        Returns True if the conversation is threaded False otherwise
      */