Update mariadb example to auto upgrade from latest image

Author: jc21

docs/advanced-config/README.md

@@ -138,6 +138,7 @@ services:
       MYSQL_USER: "npm"
       # MYSQL_PASSWORD: "npm"  # use secret instead
       MYSQL_PASSWORD__FILE: /run/secrets/MYSQL_PWD
+      MARIADB_AUTO_UPGRADE: '1'
     volumes:
       - ./mysql:/var/lib/mysql
     secrets:

docs/setup/README.md

@@ -86,6 +86,7 @@ services:
       MYSQL_DATABASE: 'npm'
       MYSQL_USER: 'npm'
       MYSQL_PASSWORD: 'npm'
+      MARIADB_AUTO_UPGRADE: '1'
     volumes:
       - ./mysql:/var/lib/mysql
 ```