message: docs: quick start retitle + note with providers link in identity docs
diff: @@ -12,7 +12,10 @@ If you want to use an auth provider to sign in users, you need to explicitly con
  it have sign-in enabled and also tell it how the external identities should
  be mapped to user identities within Backstage.
  -## Guest Sign-In Resolver
  +## Quick Start
  +
  +> See [providers](../reference/plugin-auth-backend.providers.md)
  +> for a full list of auth providers and their built-in sign-in resolvers.
  Backstage projects created with `npx @backstage/create-app` come configured with a
  sign-in resolver for GitHub guest access. This resolver makes all users share
  