Add notice for iOS beta users to update the app

public/i18n/de.json

@@ -40,7 +40,8 @@
         "ALREADY_CONNECTED": "Bereits verbunden",
         "ALREADY_CONNECTED_DETAILS": "Sie sind bereits in einem anderen Tab oder Fenster mit Threema Web verbunden!",
         "VERSION": "Version",
-        "BACKGROUND_IMAGE": "Hintergrundbild"
+        "BACKGROUND_IMAGE": "Hintergrundbild",
+        "NOTIFICATION_IOS_BETA": "Um Threema Web mit iOS zu nutzen, benötigen Sie die neueste Beta-Version (Build 2354), ältere Versionen werden nicht mehr unterstützt."
     },
     "connecting": {
         "CONNECTION_PROBLEMS": "Verbindungsprobleme",

public/i18n/en.json

@@ -40,7 +40,8 @@
         "ALREADY_CONNECTED": "Already connected",
         "ALREADY_CONNECTED_DETAILS": "You are already connected to Threema Web in another tab or window!",
         "VERSION": "Version",
-        "BACKGROUND_IMAGE": "Background Image"
+        "BACKGROUND_IMAGE": "Background Image",
+        "NOTIFICATION_IOS_BETA": "To use Threema Web on iOS, you need the newest build (2354), older builds will not work anymore."
     },
     "connecting": {
         "CONNECTION_PROBLEMS": "Connection problems",

src/partials/welcome.html

@@ -6,6 +6,10 @@
                 <p><strong translate>common.NOTE</strong> <span translate>welcome.SAFARI</span></p>
             </div>
 
+            <div class="notification">
+                <p translate>welcome.NOTIFICATION_IOS_BETA</p>
+            </div>
+
             <p class="instructions" translate>welcome.PLEASE_SCAN</p>
             <qrcode version="{{ ctrl.qrCode.version }}"
                     id="connecting-code"
@@ -28,6 +32,10 @@
         </div>
 
         <div ng-if="(ctrl.state === 'new' || ctrl.state === 'connecting') && ctrl.mode === 'unlock'" class="unlock">
+            <div class="notification">
+                <p translate>welcome.NOTIFICATION_IOS_BETA</p>
+            </div>
+
             <h2 class="instructions" translate>welcome.PLEASE_UNLOCK</h2>
             <div class="password-entry">
                 <label>