Support `localleader`

[xu-cheng]

In addition to the leader, could localleader also be supported? This would be benefit to me as I want to map my existing vim keymap to VSCode.

[dheerusri324]

Hello @J-Fields @xu-cheng ! I would like to take a crack at this issue and implement localleader support. Let me know if it's still open for contributions and if you can assign it to me!