[BRLTTY] Suggestion to add an examples for the TTY driver

[Didier Spaier]

Hey,

As I do not own (and do not know how to use) a Braille device, to test the
brltty package or its dependencies in Slint I include in /etc/brltty.conf these
two lines:
braille-driver tt
braille-device /dev/tty3

Maybe such (commented out) settings could be included in
Documents/brltty.conf.in as examples to help packagers?

Please let me know if I should provide a PR

Cheers,
Didier