title: Bottom navigation view - gradient icon tint
body: <p>I have changed icon tint in BottomNavigationView using selector and gradient color as tint when icon is pressed, but instead changing icon tint to gradient Android made all my icon purple. 
  <a href="https://i.stack.imgur.com/9oR33.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9oR33.jpg" alt="enter image description here"></a>
  My question is if there is any possibility to change tint of icons in BottomNavigationView to be gradient color?</p>
  
  <p>BottomNavigationCode:</p>
  
  <pre><code>&lt;com.google.android.material.bottomnavigation.BottomNavigationView
          android:id="@+id/nav_bottom_main"
          android:layout_width="match_parent"
          app:itemIconTint="@color/bottom_menu_background"
          android:layout_height="wrap_content"
          app:menu="@menu/bottom_navigation_main"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintEnd_toEndOf="parent"
          app:layout_constraintStart_toStartOf="parent" /&gt;
  </code></pre>
  
  <p>bottom_menu_background:</p>
  
  <pre><code> &lt;?xml version="1.0" encoding="utf-8"?&gt;
   &lt;selector xmlns:android="http://schemas.android.com/apk/res/android"&gt;
       &lt;item android:color="@color/button_gradient_blue" android:state_checked="true" /&gt;
       &lt;item android:color="@color/baseGray"/&gt;
   &lt;/selector&gt;
  </code></pre>
  
  <p>button_gradient_blue:</p>
  
  <pre><code>&lt;selector xmlns:android="http://schemas.android.com/apk/res/android" &gt;
      &lt;item android:state_pressed="true" &gt;
          &lt;shape android:shape="rectangle"  &gt;
              &lt;corners android:radius="@dimen/base_button_radius" /&gt;
              &lt;gradient android:angle="0" android:startColor="@color/light_blue_gradient_start"
              android:endColor="@color/light_blue_gradient_end"  /&gt;
          &lt;/shape&gt;
      &lt;/item&gt;
      &lt;item android:state_focused="true"&gt;
          &lt;shape android:shape="rectangle"  &gt;
              &lt;corners android:radius="@dimen/base_button_radius" /&gt;
              &lt;solid android:color="@color/button_pressed_color"/&gt;
          &lt;/shape&gt;
      &lt;/item&gt;
      &lt;item &gt;
          &lt;shape android:shape="rectangle"  &gt;
              &lt;corners android:radius="@dimen/base_button_radius" /&gt;
              &lt;gradient android:angle="0" android:startColor="@color/light_blue_gradient_start"
              android:endColor="@color/light_blue_gradient_end" /&gt;
          &lt;/shape&gt;
      &lt;/item&gt;
  &lt;/selector&gt;
  </code></pre>