Add avatar failure and avatar placeholder icon

rocket-chat-android-widgets/src/main/res/drawable/ic_avatar_failure.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:pathData="M12,12m-12,0a12,12 0,1 1,24 0a12,12 0,1 1,-24 0"
+        android:fillColor="#C2D1DA"/>
+    <path
+        android:pathData="M13.615,13.75L11.425,13.75L11.08,7L13.96,7L13.615,13.75ZM11,15.853C11,15.519 11.143,15.244 11.429,15.029C11.715,14.814 12.072,14.707 12.5,14.707C12.928,14.707 13.285,14.814 13.571,15.029C13.857,15.244 14,15.519 14,15.853C14,16.188 13.857,16.463 13.571,16.678C13.285,16.893 12.928,17 12.5,17C12.072,17 11.715,16.893 11.429,16.678C11.143,16.463 11,16.188 11,15.853Z"
+        android:fillColor="#5D8298"/>
+</vector>
\ No newline at end of file

rocket-chat-android-widgets/src/main/res/drawable/ic_avatar_placeholder.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:pathData="M3,0L21,0A3,3 0,0 1,24 3L24,21A3,3 0,0 1,21 24L3,24A3,3 0,0 1,0 21L0,3A3,3 0,0 1,3 0z"
+        android:fillColor="#C2D1DA"/>
+    <path
+        android:pathData="M11.594,11.869C12.928,11.869 14.01,10.555 14.01,8.934C14.01,7.314 13.655,6 11.594,6C9.534,6 9.178,7.314 9.178,8.934C9.178,10.555 10.26,11.869 11.594,11.869Z"
+        android:fillColor="#5D8298"/>
+    <path
+        android:pathData="M16.152,16.231C16.107,13.408 15.739,12.603 12.917,12.094C12.917,12.094 12.52,12.6 11.594,12.6C10.669,12.6 10.271,12.094 10.271,12.094C7.481,12.598 7.089,13.39 7.038,16.139C7.034,16.364 7.032,16.375 7.031,16.349C7.031,16.398 7.032,16.488 7.032,16.646C7.032,16.646 7.703,18 11.594,18C15.485,18 16.157,16.646 16.157,16.646C16.157,16.545 16.157,16.474 16.157,16.426C16.156,16.443 16.155,16.411 16.152,16.231Z"
+        android:fillColor="#5D8298"/>
+</vector>
\ No newline at end of file