Adding kibana.service file

[sergey-kalikin-adjust]

Install of kibana-bin-6.6.1 added here: #847 was failing not finding kibana.service file.

>>> Install www-apps/kibana-bin-6.6.1 into /var/tmp/portage/www-apps/kibana-bin-6.6.1/image
Traceback (most recent call last):
  File "/usr/lib/portage/python3.9/doins.py", line 609, in <module>
    sys.exit(main(sys.argv[1:]))
  File "/usr/lib/portage/python3.9/doins.py", line 598, in main
    if _doins(
  File "/usr/lib/portage/python3.9/doins.py", line 441, in _doins
    return install_runner.install_file(source, os.path.dirname(dest))
  File "/usr/lib/portage/python3.9/doins.py", line 375, in install_file
    return self._ins_runner.run(source, dest_dir)
  File "/usr/lib/portage/python3.9/doins.py", line 183, in run
    sstat = os.stat(source)
FileNotFoundError: [Errno 2] No such file or directory: b'/var/tmp/portage/www-apps/kibana-bin-6.6.1/files/kibana.service'

File was taken from here: https://github.com/gentoo/gentoo/tree/master/www-apps/kibana-bin/files