docs: improve readme

README.md

@@ -36,12 +36,17 @@ You can run this command to start serving your current working directory on 127.
 duf
 ```
 
-...or specify which folder you want to serve:
+...or specify which folder you want to serve.
 
 ```
 duf folder_name
 ```
 
+Only serve static files, disable upload and delete operations
+```
+duf --static
+```
+
 Finally, run this command to see a list of all available option
 
 

src/args.rs

@@ -31,7 +31,7 @@ fn app() -> clap::Command<'static> {
 
     let arg_static = Arg::new("static")
         .long("static")
-        .help("Only serve static files, not allowed to upload or delete file");
+        .help("Only serve static files, disable upload and delete operations");
 
     let arg_auth = Arg::new("auth")
         .short('a')