[feat] implement mariadb engine

searx/settings.yml

@@ -2031,6 +2031,16 @@ engines:
   #    query_str: 'SELECT * from mytable WHERE fieldname=%(query)s'
   #    shortcut: mysql
 
+  # Required dependency: mariadb
+  #  - name: mariadb
+  #    engine: mariadb_server
+  #    database: mydatabase
+  #    username: user
+  #    password: pass
+  #    limit: 10
+  #    query_str: 'SELECT * from mytable WHERE fieldname=%(query)s'
+  #    shortcut: mdb
+
   - name: 1337x
     engine: 1337x
     shortcut: 1337x