Changing the flow to Identifier-First

It's time to update the HTML to change the flow, in the Login form:

<fieldset>
    <label for="login_email">E-mail</label>
    <input placeholder="email" id="login_email"
        required autocomplete="webauthn username">      
    <section hidden id="login_section_password">              
        <label for="login_password">Password</label>
        <input type="password" id="login_password"
            autocomplete="webauthn current-password">
    </section>                                      
    <section hidden id="login_section_webauthn">
    </section>                                      
</fieldset>

Also, in Auth.js we will add a new top-level property and change the logic of init.

loginStep: 1,
init: () => {
    Auth.loginStep = 1;
    document.getElementById("login_section_password").hidden = true;
    document.getElementById("login_section_webauthn").hidden = true;
},