[ref] update cli description

cli/src/main.rs

@@ -23,7 +23,7 @@ static LANGUAGES_CODES: [&str; 8] = ["en", "zh_HANS", "zh_HANT", "fr", "it", "ja
 static WORD_COUNT_VALUES: [&str; 6] = ["9", "12", "15", "18", "21", "24"];
 
 #[derive(Debug, StructOpt)]
-#[structopt(name = "example", about = "An example of StructOpt usage.")]
+#[structopt(name = "dup-mnemotic", about = "DUP mnemotic generator")]
 struct Opt {
     /// Mnemotic language
     #[structopt(short = "l", long = "language", default_value = "en", possible_values = &LANGUAGES_CODES)]