check the global config for notify-cmd (#362)

This brings it in line with how notify-query works and how the wiki
defines it to also be a global option.

Co-authored-by: Clément DOUIN <soywod@users.noreply.github.com>

cli/src/config/account_config.rs

@@ -146,7 +146,11 @@ impl<'a> AccountConfig {
             downloads_dir,
             sig,
             default_page_size,
-            notify_cmd: base_account.notify_cmd.clone(),
+            notify_cmd: base_account
+                .notify_cmd
+                .as_ref()
+                .or_else(|| config.notify_cmd.as_ref())
+                .cloned(),
             notify_query: base_account
                 .notify_query
                 .as_ref()