tee.txt: standardize document format

tee.txt: standardize document format

Each text file under Documentation follows a different format. Some
doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:

- adjust identation of titles;
- mark ascii artwork as a literal block;
- adjust references.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>