fe_comment: Feedback Overview content element in the page JSON

- New content element "Feedback Overview" (CType fecomment_overview):
  the current FE user's feedback state under content.feedbackOverview,
  so the overview page renders like any other page instead of a
  front-end special case
- Rendered as USER_INT inside the cached page JSON (EXT:headless replaces
  the field per request): data is per user, visitors without a session
  get {"allowed": false} - verified that nothing leaks from the cache
- One implementation for both consumers: the new FeedbackState service
  builds the state payload; the API middleware delegates to it
- State payload (API and element) gained canSubmit and actions (all
  write endpoints with method and URL), so the front end needs no
  hard-coded endpoints for the submit button below the ticket list
- New site set evomedien/fe-comment carries the TypoScript, added to the
  site configuration; icon fecomment-overview

config/sites/vitec/config.yaml

@@ -24,6 +24,7 @@ dependencies:
   - apache-solr-for-typo3/solr-stylesheets
   - apache-solr-for-typo3/solr-bootstrap-css
   - evomedien/megamenu
+  - evomedien/fe-comment
   - vitec/quotation
   - vitec/featured-content
 frontendBase: ''