title: Avoid Chip Group to get unchecked
body: <p>I have this following Chip Group and when I tap on a Chip that is already checked, it gets unchecked, but I have to always have a checked chip. The behavior is similar to the Radio Group.</p>
  
  <pre><code>&lt;com.google.android.material.chip.ChipGroup
          android:id="@+id/chip_group_filter"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          app:checkedChip="@id/chip_1"
          app:singleSelection="true"&gt;
  
          &lt;com.google.android.material.chip.Chip
              android:id="@+id/chip_1"
              style="@style/Widget.MaterialComponents.Chip.Choice"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:text="@string/chip1"
              app:chipBackgroundColor="@color/chip_color" /&gt;
  
          &lt;com.google.android.material.chip.Chip
              android:id="@+id/chip_2"
              style="@style/Widget.MaterialComponents.Chip.Choice"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:text="@string/chip2"
              app:chipBackgroundColor="@color/chip_color" /&gt;
  
      &lt;/com.google.android.material.chip.ChipGroup&gt;
  </code></pre>