feat(gs/emacs): Add some config for vterm

for some reason installing it directly via nix doesn't work atm, so I
have this hack here

Change-Id: I45093633c35e756988078eb136c6e7bc3c532eea
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2078
Reviewed-by: glittershark <grfn@gws.fyi>
Tested-by: BuildkiteCI

users/glittershark/system/home/modules/emacs.nix

@@ -53,10 +53,15 @@ in {
       programs.emacs = {
         enable = true;
         package = pkgs.emacsUnstable;
-        extraPackages = (epkgs: with depot.tools.emacs-pkgs; [
-          dottime
-          tvl
-        ]);
+        extraPackages = (epkgs:
+          (with depot.tools.emacs-pkgs; [
+            dottime
+            tvl
+          ])
+          ++ (with depot.third_party.emacs; [
+            vterm
+          ])
+        );
       };
 
       grfn.impure.clonedRepos = {