Add project source url to synapse reverse proxy companion

roles/custom/matrix-synapse-reverse-proxy-companion/defaults/main.yml

@@ -7,6 +7,8 @@
 #
 # When Synapse workers are enabled, however, the reverse-proxying configuration is much more complicated - certain requests need to go to certain workers, etc.
 # matrix-synapse-reverse-proxy-companion is the central place services that need to reach Synapse could be pointed to.
+#
+# Project source code URL: https://github.com/nginx/nginx
 
 matrix_synapse_reverse_proxy_companion_enabled: true