feat(README): add crontab tip

README.md

@@ -14,3 +14,17 @@ Nextcloud's docker image with extra utilities
 - `ffmpeg` - Used by [Video converter](https://github.com/PaulLereverend/NextcloudVideo_Converter) app
 - `aria2` and `youtube-dl` - Used by [NCDownloader](https://github.com/shiningw/ncdownloader) app
 - `libmagickcore-dev` - To fix `Module php-imagick in this instance has no SVG support` error
+
+## Tips
+
+### Cron job
+
+If you're getting error simmilar to `Last job execution ran a day ago. Something seems wrong.`
+try to add this to your cron tab (`sudo crontab -e`):
+
+```crontab
+0,5,10,15,20,25,30,35,40,45,50,55 * * * * docker exec -u www-data <container_name> php -f /var/www/html/cron.php
+```
+
+- *Of course don't forget to change the `<container_name>` to your nextcloud's container name
+(eg. `docker-nextcloud_app`)*