Add Vcs field in the default RFS template

debexpo/templates/sponsor/rfs_template.mako

@@ -38,6 +38,7 @@ I am looking for a sponsor for my package "hello":
    Upstream Author : [fill in name and email of upstream]
  * URL             : [fill in URL of upstream's web site]
  * License         : [fill in]
+ * Vcs             : [fill in URL of packaging vcs]
 %endif
 %if c.package:
    Section         : ${ c.package.package_versions[-1].section }