feat(config): include warn by default

Signed-off-by: loongtao.zhang <[email protected]>

config.toml

@@ -1,5 +1,4 @@
 vscode_version = "1.84.2"
-autogen_warning = "# Warning, this file is autogenerated by nix4vscode. Don't modify this manually."
 
 extensions = [
   "ms-python.debugpy",

src/config.rs

@@ -14,7 +14,7 @@ pub enum ExtensionType {
     V2(String),
 }
 
-#[derive(Debug, Default, Serialize, Deserialize, Clone)]
+#[derive(Debug, Serialize, Deserialize, Clone)]
 #[serde(default)]
 pub struct Config {
     pub vscode_version: String,
@@ -25,6 +25,21 @@ pub struct Config {
     pub(crate) handled_extensions: Vec<Extension>,
 }
 
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            vscode_version: Default::default(),
+            autogen_warning: Some(
+                "# Warning, this file is autogenerated by nix4vscode. Don't modify this manually."
+                    .into(),
+            ),
+            extensions: Default::default(),
+            system: None,
+            handled_extensions: Default::default(),
+        }
+    }
+}
+
 impl Config {
     pub async fn from_file(path: &str) -> anyhow::Result<Self> {
         let content = fs::read_to_string(path).await?;