✨ feat(label_cli): implement label listing subcommand

- add `list` subcommand to `label` subcommand
- implement `run` function for `ListCli` to handle listing labels

src/config_cli/label_cli/list_cli.rs

@@ -0,0 +1,16 @@
+use clap::Parser;
+
+use cull_gmail::{Config, Result};
+
+#[derive(Debug, Parser)]
+pub struct ListCli {
+    /// Id of the rule on which action applies
+    #[clap(short, long)]
+    id: usize,
+}
+
+impl ListCli {
+    pub fn run(&self, _config: Config) -> Result<()> {
+        Ok(())
+    }
+}