Add is_dir check to auto-cd (#1506)

* Add markdown output

* Add is_dir() check

crates/nu-cli/src/cli.rs

@@ -640,6 +640,7 @@ async fn process_line(
                 }) = pipeline.commands.list[0]
                 {
                     if dunce::canonicalize(name).is_ok()
+                        && PathBuf::from(name).is_dir()
                         && which::which(name).is_err()
                         && args.list.is_empty()
                     {