README: Document branching and release policy

Due to some recent confusion while reviewing a distro packaging pull
request for flashprog, I noticed that the branching policy wasn't
explained. This is an attempt to fix that.

Change-Id: I7d776cc7499062b03cb5fb7d6bcb980670df5d04
Signed-off-by: J. Neuschäfer <j.ne@posteo.net>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/127
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Nico Huber <nico.h@gmx.de>
1 file changed