##### 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 -->

err += 'File %s already exists, but not as a directory\n' % path
                diff += 'c%s++++++.?? %s\n' % (ftype, path)
                continue
            if ftype == 'f' and not stat.S_ISREG(st.st_mode):
                change = True
                unarchived = False
                self.includes.append(path)
                err += 'Directory %s already exists, but not as a regular file\n' % path
                diff += 'c%s++++++.?? %s\n' % (ftype, path)
                continue
            if ftype == 'L' and not stat.S_ISLNK(st.st_mode):
                change = True
                self.includes.append(path)
                err += 'Directory %s already exists, but not as a symlink\n' % path
                diff += 'c%s++++++.?? %s\n' % (ftype, path)
                continue
            itemized = list('.%s.......??' % ftype)
            
            
            
            dt_object = datetime.datetime(*(time.strptime(pcs[6], '%Y%m%d.%H%M%S')[0:6]))
            timestamp = time.mktime(dt_object.timetuple())
            
            if stat.S_ISREG(st.st_mode):
                if self.module.params['keep_newer']:
                    if timestamp > st.st_mtime:
                        change = True
                        self.includes.append(path)
                        err += 'File %s is older, replacing file\n' % path
                        itemized[4] = 't'