message: docs: fix doc reference links
diff: @@ -13,9 +13,10 @@ Backstage entity by a user. The ideas here were originally proposed in the RFC
  When a user signs in to Backstage, inside the `claims` field of their Backstage
  ID Token (which are standard JWT tokens) a special `ent` field is set. `ent`
  -contains a list of [entity references](../features/software-catalog/references),
  -each of which denotes an identity or a membership that is relevant to the user.
  -There is no guarantee that these correspond to actual existing catalog entities.
  +contains a list of
  +[entity references](../features/software-catalog/references.md), each of which
  +denotes an identity or a membership that is relevant to the user. There is no
  +guarantee that these correspond to actual existing catalog entities.
  Let's take an example sign-in resolver for the Google auth provider and explore
  how the `ent` field inside `claims` can be set.
  