Add example to the user guide: how to list a job's files

Example script

```python
import humanize
from tabulate import tabulate

from ansys.hps.client import Client, ProjectApi

project_id = "02vna3Aap8ZEkykK0j52Uj"
job_id = "02vna3DVqDW2CgQrRe3X34"
cl = Client(
url="https://localhost:8443/hps",
username="repuser",
password="repuser",
verify=False
)

project_api = ProjectApi(cl, project_id)

job = project_api.get_jobs(id=[job_id], fields=["id", "file_ids"])[0]
query_params = {"id": job.file_ids, "hash.ne": "null"}
files = project_api.get_files(**query_params)

table_data = [['Name', 'Path', 'Size', 'Last Modified']]
table_data.extend(
[[
f.name,
f.evaluation_path,
humanize.naturalsize(f.size),
humanize.naturaltime(f.modification_time)
] for f in files]
)
print(tabulate(table_data, headers="firstrow"))
```

Locate the user guide entry point and add the supplied Python example for listing a job's files. Check that the example is formatted as a readable guide section and that it clearly demonstrates retrieving the job's file IDs, querying files, and printing their names, paths, sizes, and modification times.

Written by the indexing model from the issue text.