add cli arg to set timetable padding

src/cli.rs

@@ -20,6 +20,10 @@ pub struct Args {
     #[arg(short, long)]
     pub date: Option<String>,
 
+    /// number of preceding and succeeding time records in the timetable
+    #[arg(short, long, default_value_t = 5)]
+    pub padding: i8,
+
     #[arg(short, long, default_value = "Local")]
     pub local: String,