feat: add compose ps command

Ps is new command scoped under compose. It is just proxy to `docker
compose ps`.

src/command_builder.rs

@@ -63,7 +63,7 @@ impl CommandBuilder {
     }
 
     fn build(self) -> Result<Command> {
-        debug_println!("\nran {self}\n");
+        debug_println!("-----\n{self}\n-----");
 
         let (first, rest) = self.args.split_first().context("empty args")?;
         let mut command = Command::new(first);