feat(grfn/web): Link to my own version of my pubkey

the keys.gnupg.net keyserver has been down for some time now, let's not
link to that in favor of linking to a self-hosted version of my GPG
public key

Change-Id: I9f645c562c2b04e9fb755f21d1ec8a89f89c2230
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10032
Tested-by: BuildkiteCI
Autosubmit: grfn <grfn@gws.fyi>
Reviewed-by: grfn <grfn@gws.fyi>

users/grfn/web/default.nix

@@ -26,6 +26,7 @@ let
       cp -r ${site.recipes} $out/recipes
       cp ${resume} $out/resume.pdf
       cp ${keys} $out/keys
+      cp ${./pubkey.gpg} $out/pubkey.gpg
     '';
 
   purge-cf = writeShellApplication {