Add an in-process post event bus (#13)

Handlers emit PostCreated and PostUpdated after a successful write. Store writes do not publish, and hidden roots are skipped.

Reviewed-on: #13
Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/web/posts.go

@@ -85,6 +85,7 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 	if parent != nil {
 		s.notifyPostReply(parent, root, post, user)
 	}
+	s.publishPostCreated(post, root, user)
 	http.Redirect(
 		w,
 		r,
@@ -190,6 +191,7 @@ func (s *Server) handleEditPost(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "could not save post", http.StatusInternalServerError)
 		return
 	}
+	s.publishPostUpdated(post, root, nil)
 	http.Redirect(
 		w,
 		r,