Center icon of the send msg button

[aleexgheorghe]

Temporary solution proposed (res/layout/activity_chat.xml:55):

    <Button
        android:id="@+id/btnSendMsg"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginStart="8dp"
        android:layout_weight="9"
        android:gravity="center_horizontal"
        android:paddingStart="20dp"
        android:background="@drawable/msg_bar_send"
        android:isScrollContainer="false"
        app:backgroundTint="#09a984"
        app:icon="@drawable/baseline_send_24" />

It is not correct to center a button with a paddinStart, we should check a much more optimal solution.