Feat: js flow api sdk

[bjoern-m]

Description

This PR introduces a new TypeScript-based SDK for managing authentication flows with Hanko.

Key Features

• State Management: The State class encapsulates flow states with properties like name, payload, actions, and csrfToken. It supports initialization, serialization (save/load), and event dispatching for state changes.
• Action Execution: The Action class enables type-safe action invocation.
• Auto-Stepping: Automatically progresses through predefined states via autoSteps, with configurable exclusion options.
• Passkey Autofill: Integrates passkey autofill activation handlers for supported states.
• Persistence: Serializes state to localStorage.

Example Usage:

const hanko = new Hanko(/* params */);
const state = await hanko.createState("login");

await state.actions.continue_with_login_identifier.run({
  username: "user",
});

hanko.onBeforeStateChange(({state}) => {
  console.log(`action has been invoked ${state.invokedAction.name}`);
});

hanko.onAfterStateChange(({state}) => {
  console.log(`action has been finished ${state.previousAction.name}`);

  if (state.name == "login_init") {
    state.passkeyAutofillActivation();
  }
});

Todos

• Support for IdP-initiated SAML sign-in
• Readme