Add gcsfuse example to the samples

the only gcsfuse example was deleted when removing the apache-php sample. https://github.com/google/kctf/blob/57e59756cbe081ff922abc2004a9d168492e4b25/samples/apache-php/challenge.yaml has an example. we should also update the web template with a php and python sample server so people know how to use it.

```yaml
podTemplate:
template:
spec:
containers:
- name: challenge
volumeMounts:
- name: sessions
mountPath: /mnt/disks/sessions
- name: uploads
mountPath: /mnt/disks/uploads
volumes:
- name: sessions
persistentVolumeClaim:
claimName: apache-php-sessions
- name: uploads
persistentVolumeClaim:
claimName: apache-php-uploads
persistentVolumeClaims:
- apache-php-sessions
- apache-php-uploads
```