[SDK-4026] Add some examples

[adamjmcgrath]

Examples

• Authentication Client
  • Signup a user
  • Use a client assertion
  • Use Refresh Tokens
  • Complete the Authorization Code flow with PKCE
  • Login with Passwordless
• Management Client
  • Paginate through a list of users
  • Paginate through a list of logs using checkpoint pagination
  • Import users from a JSON file
  • Update a user's user_metadata