Hi! 👋 When `base_keymap` is set to `None`, it disables all the
keybindings, even if `vim_mode` or `helix_mode` is enabled. However, I
think the Vim/Helix keybindings should be applied on top of the empty
base keymap.

My use case for this is to start with the minimal set of Vim/Helix key
shortcuts and add other bindings on top of that, instead of flooding the
keymap with hundreds of predefined shortcuts from some base keymap.