DeepL: added Arabic

app/src/main/assets/deepl.json

@@ -1,4 +1,9 @@
 [
+  {
+    "language": "AR",
+    "name": "Arabic",
+    "supports_formality": false
+  },
   {
     "language": "BG",
     "name": "Bulgarian",

app/src/main/java/eu/faircode/email/DeepL.java

@@ -115,7 +115,9 @@ public class DeepL {
                 int frequency = prefs.getInt("translated_" + target, 0);
 
                 String flag;
-                if ("CS".equals(target))
+                if ("AR".equals(target))
+                    flag = "SA";
+                else if ("CS".equals(target))
                     flag = "CZ";
                 else if ("DA".equals(target))
                     flag = "DK";