package/c-capnproto: add an upstream URL to Config.in

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>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/c-capnproto/Config.in

@@ -12,6 +12,8 @@ config BR2_PACKAGE_C_CAPNPROTO
 	  plugin for C. Requires regular Cap'n Proto and only
 	  provides serialization (no RPC).
 
+	  https://github.com/opensourcerouting/c-capnproto
+
 comment "c-capnproto needs host and target gcc >= 5 w/ C++14, threads, atomic"
 	depends on BR2_USE_MMU
 	depends on!BR2_HOST_GCC_AT_LEAST_5 || \