The config directory in the container is /app/config.
Run the container with a volume for the config and one or more volumes for the shared data. You may also want to run the container with a uid and gid from your host system.
docker run -d --restart always \
--name syncthing \
-p 8384:8384 \
-p 22000:22000 \
-v /config/dir/on/host:/app/config \
-v /data/dir/on/host:/data/dir/in/container \
tortxof/syncthing