Add hint to sign in with 2FA enabled

lib/l10n/app_en.arb

@@ -245,6 +245,10 @@
 	"@signInHeaderText": {
 		"description": "Inform user what to do in sign in widget"
 	},
+	"signIn2faHintText": "*Use an app password if you have two-factor authentication enabled in the server",
+	"@signIn2faHintText": {
+		"description": "Notify users with 2FA enabled what should be done in order to sign in correctly"
+	},
 	"serverAddressInputHint": "Sever address",
 	"@serverAddressInputHint": {
 		"description": "Hint of the text field expecting server address data"

lib/widget/sign_in.dart

@@ -63,6 +63,17 @@ class _SignInState extends State<SignIn> {
                           child: _buildForm(context),
                         ),
                       ),
+                      Container(
+                        alignment: AlignmentDirectional.centerStart,
+                        constraints: const BoxConstraints(
+                            maxWidth: AppTheme.widthLimitedContentMaxWidth),
+                        padding: const EdgeInsets.symmetric(
+                            horizontal: 32, vertical: 16),
+                        child: Text(
+                          AppLocalizations.of(context).signIn2faHintText,
+                          style: TextStyle(fontStyle: FontStyle.italic),
+                        ),
+                      ),
                       if (!platform_k.isWeb) Expanded(child: Container()),
                       Container(
                         constraints: const BoxConstraints(