feat(3p/dfmt): Add derivation for the D code formatter

Change-Id: I4e06676f45df334db4fbc4f1657a6f16828547dc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3727
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

users/tazjin/nixos/tverskoy/default.nix

@@ -237,6 +237,7 @@ in lib.fix(self: {
       screenLock
       tools.nsfv-setup
       users.tazjin.emacs
+      third_party.dfmt
     ]) ++
 
     # programs from nixpkgs
@@ -245,7 +246,6 @@ in lib.fix(self: {
       chromium
       curl
       ddcutil
-      dfmt
       direnv
       dmd
       dnsutils