Added automatic charset option

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

@@ -6084,6 +6084,9 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                 protected void onExecuted(Bundle args, SortedMap<String, Charset> charsets) {
                     PopupMenuLifecycle popupMenu = new PopupMenuLifecycle(context, powner, ibMore);
 
+                    popupMenu.getMenu().add(Menu.NONE, 0, 0, R.string.title_charset_auto)
+                            .setIntent(new Intent().putExtra("charset", (String) null));
+
                     int order = 0;
                     for (String name : charsets.keySet()) {
                         order++;

app/src/main/res/values/strings.xml

@@ -1473,6 +1473,7 @@
     <string name="title_thread_info" translatable="false">Thread info</string>
     <string name="title_resync">Resync</string>
     <string name="title_charset">Encoding</string>
+    <string name="title_charset_auto">Automatic</string>
     <string name="title_alternative_text">Show plain text</string>
     <string name="title_alternative_html">Show HTML</string>
     <string name="title_no_openpgp">OpenKeychain not found</string>