RBS: Decleare Profile#profile_badges manually

As a preparation of giving types to controllers, this adds types for
`Profile#profile_badges` manually because current rbs_rails does not
support HABTM association.  It should be removed if rbs_rails will
support it in the future.

refs: pocke/rbs_rails#272

sig/handwritten/app/models/profile.rbs

@@ -1,4 +1,9 @@
 class Profile < ::ApplicationRecord
+  # NOTE: This method has been declared manually because current rbs_rails does not support HABTM.
+  #       It should be removed if rbs_rails will support it.
+  #       refs: https://github.com/pocke/rbs_rails/pull/272
+  def profile_badges: () -> ProfileBadge::ActiveRecord_Associations_CollectionProxy
+
   def ensure_image_from_github: () -> void
 
   private def fetch_profile_image_from_github: () -> untyped