Merge branch 'docs-link-development-policies' into 'master'

Docs: Link to DeclarativePolicy framework from development guide

See merge request gitlab-org/gitlab-ce!22348

doc/development/README.md

@@ -50,6 +50,7 @@ description: 'Learn how to contribute to GitLab.'
 - [Permissions](permissions.md)
 - [Prometheus metrics](prometheus_metrics.md)
 - [Guidelines for reusing abstractions](reusing_abstractions.md)
+- [DeclarativePolicy framework](policies.md)
 
 ## Performance guides