Show in action bar when composing plain text message

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

@@ -776,6 +776,7 @@ public class FragmentCompose extends FragmentBase {
     public void onPrepareOptionsMenu(Menu menu) {
         super.onPrepareOptionsMenu(menu);
 
+        menu.findItem(R.id.menu_plain_icon).setVisible(state == State.LOADED && plain_only);
         menu.findItem(R.id.menu_zoom).setVisible(state == State.LOADED);
         menu.findItem(R.id.menu_media_toolbar).setVisible(state == State.LOADED);
         menu.findItem(R.id.menu_clear).setVisible(state == State.LOADED);

app/src/main/res/menu/menu_compose.xml

@@ -1,6 +1,13 @@
 <?xml version="1.0" encoding="utf-8"?>
 <menu xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto">
+    <item
+        android:id="@+id/menu_plain_icon"
+        android:icon="@drawable/baseline_notes_24"
+        android:title="@string/title_send_plain_text"
+        android:visible="false"
+        app:showAsAction="always" />
+
     <item
         android:id="@+id/menu_zoom"
         android:icon="@drawable/baseline_format_size_24"