rPackages.extrafont: libraries don't register correctly

[jkorinth]

Describe the bug
Library packages for R (and presumably similarly structured ones) are not registered correctly inside the devshell.

To Reproduce

Steps to reproduce the behavior:

1. Have devshell with devshell.toml:

[devshell]
packages = [ "R", "rPackages.extrafont" ]

2. nix develop then R, try loadlibrary("extrafont").

Result:
Error in library("extrafont") : there is no package called ‘extrafont’

Expected behavior

Should work the same as in nix-shell -p R -p rPackages.extrafont, where you get
Registering fonts with R instead.

System information

Inputs:
├───devshell: github:numtide/devshell/12e914740a25ea1891ec619bb53cf5e6ca922e40
│   ├───flake-utils: github:numtide/flake-utils/4022d587cbbfd70fe950c1e2083a02621806a725
│   │   └───systems: github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e
│   └───nixpkgs: github:NixOS/nixpkgs/63143ac2c9186be6d9da6035fa22620018c85932
├───flake-compat: github:edolstra/flake-compat/0f9255e01c2351cc7d116c072cb317785dd33b33
├───flake-utils: github:numtide/flake-utils/b1d9ab70662946ef0850d488da1c9019f3a9752a
│   └───systems: github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e
└───nixpkgs: path:/nix/store/gig8j85kj7ybjy3ksn6k3aich8j2k59y-source?lastModified=0&narHash=sha256-6hqgQ8OK6gsMu1VtcGKBxKQInRLHtzulDo9Z5jxHEFY%3D