Shift+8 keybind missing in helix/select mode

In helix/select mode, Shift+8 should map to smart selection, the same as [in normal mode](https://github.com/71/dance/blob/master/extensions/helix/package.json?plain=1#L1308-L1313). Currently, it is [ignored](https://github.com/71/dance/blob/master/extensions/helix/package.json?plain=1#L2285-L2289).