vim: add keybinding to jump to parent directory in project panel (#11078)

Release Notes:

- vim: Support `-` to go to `parent directory` of the project panel.

As mentioned in the comments of #11073 this adds support for netrw's `-`
to go to the parent directory in the project panel. Again tested on
linux only.


- N/A

assets/keymaps/vim.json

@@ -627,7 +627,8 @@
       "p": "project_panel::Open",
       "x": "project_panel::RevealInFinder",
       "shift-g": "menu::SelectLast",
-      "g g": "menu::SelectFirst"
+      "g g": "menu::SelectFirst",
+      "-": "project_panel::SelectParent"
     }
   }
 ]