Add a `rustfmt` config to my dotfiles, though admittedly I'm not sure if it completely works.

home/home.nix

@@ -18,6 +18,7 @@
     ./dotfiles.nix # home.file
     ./variables.nix # home.sessionVariables
     ./aliases.nix # home.shellAliases
+    ./rust.nix # Should be my `rustfmt` config.
   ];
 
   home = {

home/rust.nix

@@ -0,0 +1,15 @@
+{
+  xdg.configFile = {
+    rustfmt = {
+      enable = true;
+      target = "rustfmt/rustfmt.toml";    
+      text = ''
+          tab_spaces = 2
+          hard_tabs = false
+          # indent_style = "Block"
+            # TODO: "Unstable" as of rustfmt 1.7.0
+          reorder_imports = true
+      '';
+    };
+  };
+}