Bump notebook version 1.0.0 -> 2.0.0 (#236)

Author: davidbrochart

javascript/src/ynotebook.ts

@@ -69,7 +69,7 @@ export class YNotebook
   /**
    * Document version
    */
-  readonly version: string = '1.0.0';
+  readonly version: string = '2.0.0';
 
   /**
    * Creates a standalone YNotebook

jupyter_ydoc/ynotebook.py

@@ -65,7 +65,7 @@ def version(self) -> str:
         :return: Document's version.
         :rtype: str
         """
-        return "1.0.0"
+        return "2.0.0"
 
     @property
     def ycells(self):