Add drawables.

rocket-chat-android-widgets/src/main/res/drawable/ic_attach_file_black_24dp.xml

+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M16.5,6v11.5c0,2.21 -1.79,4 -4,4s-4,-1.79 -4,-4V5c0,-1.38 1.12,-2.5 2.5,-2.5s2.5,1.12 2.5,2.5v10.5c0,0.55 -0.45,1 -1,1s-1,-0.45 -1,-1V6H10v9.5c0,1.38 1.12,2.5 2.5,2.5s2.5,-1.12 2.5,-2.5V5c0,-2.21 -1.79,-4 -4,-4S7,2.79 7,5v12.5c0,3.04 2.46,5.5 5.5,5.5s5.5,-2.46 5.5,-5.5V6h-1.5z"/>
+</vector>

rocket-chat-android-widgets/src/main/res/drawable/top_shadow.xml

+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item>
+        <shape android:shape="rectangle">
+            <solid android:color="@color/colorShadow" />
+        </shape>
+    </item>
+
+    <item android:top="1dp">
+        <shape android:shape="rectangle">
+            <solid android:color="@android:color/white" />
+        </shape>
+    </item>
+</layer-list>
\ No newline at end of file