##### 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 -->

- Can handle I(.zip) files using C(unzip) as well as I(.tar), I(.tar.gz), I(.tar.bz2) and I(.tar.xz) files using C(gtar).
    - Does not handle I(.gz) files, I(.bz2) files or I(.xz) files that do not contain a I(.tar) archive.
    - Uses gtar's C(--diff) arg to calculate if changed or not. If this C(arg) is not
      supported, it will always unpack the archive.
    - Existing files/directories in the destination which are not in the archive
      are not touched. This is the same behavior as a normal archive extraction.
    - Existing files/directories in the destination which are not in the archive
      are ignored for purposes of deciding if the archive should be unpacked or not.
seealso:
- module: community.general.archive
- module: community.general.iso_extract
- module: community.windows.win_unzip
author: Michael DeHaan
'''
EXAMPLES = r'''
- name: Extract foo.tgz into /var/lib/foo
  unarchive:
    src: foo.tgz
    dest: /var/lib/foo
- name: Unarchive a file that is already on the remote machine
  unarchive:
    src: /tmp/foo.zip
    dest: /usr/local/bin
    remote_src: yes
- name: Unarchive a file that needs to be downloaded (added in 2.0)
  unarchive:
    src: https://example.com/example.zip
    dest: /usr/local/bin
    remote_src: yes
- name: Unarchive a file with extra options