docs: update README with note about disabling email enumeration protection on firebase project

Author: russellwheatley

FirebaseSwiftUI/README.md

@@ -132,6 +132,7 @@ struct ContentView: View {
     // Create configuration with options
     let configuration = AuthConfiguration(
       shouldAutoUpgradeAnonymousUsers: true,
+      legacyFetchSignInWithEmail: true,
       tosUrl: URL(string: "https://example.com/tos"),
       privacyPolicyUrl: URL(string: "https://example.com/privacy"),
       emailLinkSignInActionCodeSettings: actionCodeSettings,
@@ -829,6 +830,7 @@ public struct AuthConfiguration {
     shouldHideCancelButton: Bool = false,
     interactiveDismissEnabled: Bool = true,
     shouldAutoUpgradeAnonymousUsers: Bool = false,
+    legacyFetchSignInWithEmail: Bool = false,
     customStringsBundle: Bundle? = nil,
     tosUrl: URL? = nil,
     privacyPolicyUrl: URL? = nil,
@@ -850,6 +852,7 @@ public struct AuthConfiguration {
 | `shouldHideCancelButton` | `Bool` | `false` | When `true`, hides the cancel button in auth flows, preventing users from dismissing the UI. Useful for mandatory authentication. |
 | `interactiveDismissEnabled` | `Bool` | `true` | When `false`, prevents users from dismissing auth sheets by swiping down. |
 | `shouldAutoUpgradeAnonymousUsers` | `Bool` | `false` | When `true`, automatically links anonymous user accounts with new sign-in credentials, preserving any data associated with the anonymous session. |
+| `legacyFetchSignInWithEmail` | `Bool` | `false` | When `true`, wrong-provider failures can look up the email's existing sign-in methods and present a recovery modal with matching enabled sign-in options. Email enumeration protection must be disabled on your Firebase project for this to work. |
 | `customStringsBundle` | `Bundle?` | `nil` | Custom bundle for string localizations. Allows you to override default strings with your own translations. |
 | `tosUrl` | `URL?` | `nil` | URL to your Terms of Service. When both `tosUrl` and `privacyPolicyUrl` are set, links are displayed in the auth UI. |
 | `privacyPolicyUrl` | `URL?` | `nil` | URL to your Privacy Policy. When both `tosUrl` and `privacyPolicyUrl` are set, links are displayed in the auth UI. |