docs: Update running_rune_with_occlum.md
Add command to launch a CentOS 7.5 container
Update Occlum SDK container image to 0.14.0
- Assume the host system is CentOS 7.5.
- You can also launch a CentOS 7.5 container as your host system with the following command:
```shell
-
+ docker run -it --privileged --device /dev/isgx centos:7.5.1804
```
If so, you need to run **another docker daemon** inside this CentOS 7.5 container. Please refer to [this guide](https://docs.docker.com/engine/install/centos) to install docker daemon, and type the following command to start dockerd.
```shell
mkdir "$HOME/rune_workdir"
docker run -it --privileged --device /dev/isgx \
-v "$HOME/rune_workdir":/root/rune_workdir \
- occlum/occlum:0.13.0-centos7.5
+ occlum/occlum:0.14.0-centos7.5
```
### Prepare the materials
