mihon/app/src/main/res/menu/reader.xml

<?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/action_bookmark"
        android:icon="@drawable/ic_bookmark_border_24dp"
        android:title="@string/action_bookmark"
        app:iconTint="?attr/colorOnToolbar"
        app:showAsAction="ifRoom" />

    <item
        android:id="@+id/action_remove_bookmark"
        android:icon="@drawable/ic_bookmark_24dp"
        android:title="@string/action_remove_bookmark"
        app:iconTint="?attr/colorOnToolbar"
        app:showAsAction="ifRoom" />

</menu>