docs/manual: update contribute.txt to cover get-developers

This commit updates the contribute.txt part of the manual to tell
people to use get-developers to get the appropriate "git send-email"
command when sending patches.

[Peter: use --cc instead of --to as suggested by Yann/Arnout]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/manual/contribute.txt

@@ -283,10 +283,18 @@ automatically adding the +Signed-off-by+ line.
 Once patch files are generated, you can review/edit the commit message
 before submitting them, using your favorite text editor.
 
-Lastly, send/submit your patch set to the Buildroot mailing list:
+Buildroot provides a handy tool to know to whom your patches should be
+sent, called +get-developers+. This tool reads your patches and
+outputs the appropriate +git send-email+ command to use:
 
 ---------------------
-$ git send-email --to buildroot@buildroot.org outgoing/*
+$ ./support/scripts/get-developers outgoing/*
+---------------------
+
+Use the output of +get-developers+ to send your patches:
+
+---------------------
+$ git send-email --to buildroot@buildroot.org --cc bob --cc alice outgoing/*
 ---------------------
 
 Note that +git+ should be configured to use your mail account.