fix(): adds user to default ftp group

src/docker-entrypoint.sh

@@ -1,18 +1,15 @@
 #!/bin/sh
 
-addgroup \
-	-S \
-	$FTP_USER
 
 adduser \
 	-D \
-	-G $FTP_USER \
+	-G ftp \
 	-h /home/$FTP_USER \
 	-s /bin/false \
 	$FTP_USER
 
 mkdir -p /home/$FTP_USER
-chown -R $FTP_USER:$FTP_USER /home/$FTP_USER
+chown -R $FTP_USER:ftp /home/$FTP_USER
 echo "$FTP_USER:$FTP_PASS" | /usr/sbin/chpasswd
 
 exec "$@"