##### SUMMARY
The unarchive module is missing documentation on its return values.
Only the `list_files` option mentions it at all:
> If set to True, return the list of files that are contained in the tarball.

It does not mention how this list is returned (Spoiler: It's in the `files` key, as a list of file names).
A `RETURN` section should be added to the module documentation.
Ideally, the `EXAMPLES` section should be extended to include one or two examples that use the return values somehow.

##### ISSUE TYPE
- Documentation Report

##### COMPONENT NAME
modules/files/unarchive.py

##### ANSIBLE VERSION

```
ansible 2.9.2
  config file = None
  configured module search path = ['/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib64/python3.6/site-packages/ansible
  executable location = /usr/lib/python-exec/python3.6/ansible
  python version = 3.6.9 (default, Oct  5 2019, 11:39:46) [GCC 8.3.0]
```

##### CONFIGURATION
not relevant

##### OS / ENVIRONMENT
not relevant

##### ADDITIONAL INFORMATION
<!--- Describe how this improves the documentation, e.g. before/after situation or screenshots -->

<!--- HINT: You can paste gist.github.com links for larger files -->

module = AnsibleModule(
        
        argument_spec=dict(
            src=dict(type='path', required=True),
            dest=dict(type='path', required=True),
            remote_src=dict(type='bool', default=False),
            creates=dict(type='path'),
            list_files=dict(type='bool', default=False),
            keep_newer=dict(type='bool', default=False),
            exclude=dict(type='list', elements='str', default=[]),
            extra_opts=dict(type='list', elements='str', default=[]),
            validate_certs=dict(type='bool', default=True),
        ),
        add_file_common_args=True,
        
        supports_check_mode=True,
    )
    src = module.params['src']
    dest = module.params['dest']
    b_dest = to_bytes(dest, errors='surrogate_or_strict')