feat: introduce treefmt and fmt all

.vscode/settings.json

@@ -1,4 +1,9 @@
 {
+    "editor.defaultFormatter": "ibecker.treefmt-vscode",
+    "treefmt.command": "treefmt",
+    "editor.formatOnSave": true,
+    "nix.enableLanguageServer": true,
+    "nix.serverPath": "nil",
     "nix.serverSettings": {
         // settings for 'nil' LSP
         "nil": {
@@ -9,11 +14,14 @@
                     "unused_with"
                 ]
             },
-            "formatting": {
-                "command": [
-                    "treefmt-nix",
-                ]
-            }
+            // TODO: this doesn't work because treefmt-nix wants the output path as an argument
+            // "formatting": {
+            //     "command": [
+            //         "treefmt-nix",
+            //         "--stdin",
+            //         "/dev/stdout"
+            //     ]
+            // }
         }
     },
 }