docs: clarify 12am/12pm meaning in English schedules

Author: aster-void

README.md

@@ -268,6 +268,7 @@ Full form:
 **Schedule**: Cron or English phrase
 - Cron: `min hour day month weekday` (e.g., `*/5 * * * *` = every 5 minutes)
 - English: `every 5 minutes`, `every day at 4:00 pm`, `7pm every Thursday`, `Sunday at 12:00`, `midnight on Tuesdays`
+- Note: `12 am` = midnight (00:00), `12 pm` = noon (12:00)
 
 ### Environment variable priority