Accept Neovim notifications with unknown arguments
Accept Neovim notifications with unknown arguments

See #267/api-contract. There is no point in being too strict when
validating API notifications, this way Neovim can change the API
without breakage on our side.

This immediately applies to the mode_change notification, that now
includes an additional argument. We don't yet handle the additional
argument but there is no reason to reject argument already support.

equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt