add lines on the necessity of known hosts

# How to work with Jupyter everywhere

./run_chromium_through_ssh_tunnel.sh user@host.example.com

```

Note that these steps will only work, if `host.example.com` is a known host in 

`.ssh/known_hosts`. (To test this, simply create a ssh connection to 

`host.example.com`, if it is not yet a known host, you will be asked whether to 

continue and if you do, `host.example.com` will be added to `.ssh/known_hosts`.)

### Connect your browser to the remote Jupyterlab