Emacs: Adding Tab and Shift-Tab to Browse Kill Ring

The Browse Kill Ring Extension is great:

christopher@theoden ~$ guix show emacs-browse-kill-ring 
name: emacs-browse-kill-ring
version: 2.0.0-0.1ef72cc
outputs: out
systems: x86_64-linux i686-linux
dependencies: 
location: gnu/packages/emacs-xyz.scm:22330:4
homepage: https://github.com/browse-kill-ring/browse-kill-ring
license: GPL 2+
synopsis: Interactively insert items from kill-ring  
description: Did you ever feel that `C-y M-y M-y M-y ...' is not a great way of trying to find that piece of text you know you killed a while back? Then
+ `browse-kill-ring.el' is for you.

The obvious thing that is missing, however, is an easy way to jump to the next kill ring entry once you are in the Kill Ring buffer. These .emacs additions allow you to use TAB and SHIFT-TAB for that purpose:

(define-key browse-kill-ring-mode-map
  (kbd "") #'browse-kill-ring-forward)

(define-key browse-kill-ring-mode-map
  (kbd "") #'browse-kill-ring-previous)