Add the new command 'Attach Source' to the readme (#713)

Signed-off-by: Jinbo Wang <jinbwan@microsoft.com>

Author: testforstephen

README.md

@@ -59,10 +59,11 @@ The following commands are available:
 - `Java:Force Java compilation` (`Shift+Alt+B`): manually triggers compilation of the workspace.
 - `Java:Organize imports` (`Shift+Alt+O`): Organize imports in the currently opened Java file.
 - `Java:Open Java formatter settings`: Open the Eclipse formatter settings. Creates a new settings file if none exists.
-
-*New in 0.33.0:*
 - `Java:Clean the Java language server workspace`: Clean the Java language server workspace.
 
+*New in 0.34.0:*
+- `Java:Attach Source`: Attach a jar/zip source to the currently opened binary class file. This command is only available in the editor context menu.
+
 Supported VS Code settings
 ==========================
 The following settings are supported: