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>
diff --git a/README b/README
index e993a60..01e96c6 100644
--- a/README
+++ b/README
@@ -179,6 +179,16 @@
 by adding sudo in front of the commands above.
 
 
+Branching and release policy
+----------------------------
+
+- Feature development happens on the `main` branch
+- Branch-off points for releases are tagged with tags that start with `p`, such as `p1.0`
+- Release branches have a `.x` suffix, for example `1.0.x`
+- Release tags start with `v`, for example `v1.0` or `v1.0.1`
+- Release candidate tags additionally end with `-rcN`, for example `v1.0-rc1`
+
+
 Contact
 -------