This displays how users can configure an impure evaluation for
tvix-serde, which makes it possible to use e.g. `nixpkgs/lib`.
We might want to add an example showing how the full Nix-glue
compatibility stuff can be added here, too.
Change-Id: I2224a3fc66e739969d4c723c3d9d8127a046b6fd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10994
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
