Fix CSP for disqus and Google Analytics

This commit should fix existing problems with Disqus and Google
Analytics enabled in the meta-yaml section of a note.

Before this commit they were blocked by the strict CSP. It's still
possible to disable the added directives using `addDisqus` and
`addGoogleAnalytics` in the `csp` config section.

They are enabled by default to prevent breaking changes.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

lib/config/default.js

@@ -18,6 +18,8 @@ module.exports = {
     directives: {
     },
     addDefaults: true,
+    addDisqus: true,
+    addGoogleAnalytics: true,
     upgradeInsecureRequests: 'auto',
     reportURI: undefined
   },