Update README.md

Author: ethanflower1903

README.md

@@ -66,7 +66,7 @@ Database:
 ```console
 $ docker run -d \
 -v db:/var/lib/mysql \
-mariadb:10.5
+mariadb:10.5///
 ```
 
 If you want to get fine grained access to your individual files, you can mount additional volumes for data, config, your theme and custom apps. The `data`, `config` files are stored in respective subfolders inside `/var/www/html/`. The apps are split into core `apps` (which are shipped with Nextcloud and you don't need to take care of) and a `custom_apps` folder. If you use a custom theme it would go into the `themes` subfolder.