Documentation looks uncomplete

The documentation mentions the image being available on Docker Hub,

but there is basically no documentation on the setup using the prebuld image (such as volumes, if any?).

currently i have this

```bash
IMAGE="docker.io/cryptpad/cryptpadlatest"
CONT_NAME="cryptpad"
root_conf_path="[...]/cryptpad/"
touch $root_conf_path/config.js

podman run \
--name $CONT_NAME \
--detach \
--restart always \
-p 3000:3000 \
-p 3003:3003 \
-v "$root_conf_path/config.js:/cryptpad/config/config.js" \
-v "$root_conf_path/data/blob:/cryptpad/blob" \
-v "$root_conf_path/data/block:/cryptpad/block" \
-v "$root_conf_path/data/data:/cryptpad/data" \
-v "$root_conf_path/data/files:/cryptpad/datastore" \
-v "$root_conf_path/customize:/cryptpad/customize" \
-v "$root_conf_path/onlyoffice-dist:/cryptpad/www/common/onlyoffice/dist" \
-v "$root_conf_path/onlyoffice-conf:/cryptpad/onlyoffice-conf" \
"$IMAGE"
```

```
cp: can't create '': No such file or directory

####################################################################
Warning: No config file provided for cryptpad
We will create a basic one for now but you should rerun this service
by providing a file with your settings
eg: docker run -v /path/to/config.js:/cryptpad/config/config.js
####################################################################
```