Add support for display name, initial value and url parameters

[ajayyy]

• displayName (string) - Display name of user, useful when using guest accounts
• composerIntialValue (string) - Initial value of the composer for prepoulating a sample message
• signInPrompt (string) - Show sign in prompts
  • 'none' - Never show (default)
  • 'guests' - Show if signed in as guest
  • 'all' - Always show
• urlParameters (boolean) - Allow adding to config with url prameters (#displayName=Something)
  • 'true' (default)
  • 'false'