Add an upstream URL to the help text in Config.in. This
addresses the 'Missing' URL status in the package stats
web page output.
Signed-off-by: Mark Corbin <mark@dibsco.co.uk> Reviewed-by: Peter Seiderer <ps.report@gmx.net> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>