Add single cookie consent api URLs

- once the single consent API is enabled on GOV.UK the JS will be making XMLHttprequests to the staging and production environments for the single consent api, so these URLs need to be added to the CSP

lib/govuk_app_config/govuk_content_security_policy.rb

@@ -71,7 +71,9 @@ def self.build_policy(policy)
                        *GOVUK_DOMAINS,
                        *GOOGLE_ANALYTICS_DOMAINS,
                        # Speedcurve real user monitoring (RUM) - as per: https://support.speedcurve.com/docs/add-rum-to-your-csp
-                       "lux.speedcurve.com"
+                       "lux.speedcurve.com",
+                       "gds-single-consent-staging.app",
+                       "gds-single-consent.app"
 
     # Disallow all <object>, <embed>, and <applet> elements
     #