For #8469 - Support rtl for onboarding - theme picker

We'll mirror the theme picker images and make sure the radio buttons are
positioned correctly in relation to them.

app/src/main/res/drawable/ic_onboarding_dark_theme.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<bitmap xmlns:android="http://schemas.android.com/apk/res/android"
+        android:src="@drawable/onboarding_dark_theme"
+        android:autoMirrored="true">
+</bitmap>

app/src/main/res/drawable/ic_onboarding_light_theme.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<bitmap xmlns:android="http://schemas.android.com/apk/res/android"
+        android:src="@drawable/onboarding_light_theme"
+        android:autoMirrored="true">
+</bitmap>

app/src/main/res/layout/onboarding_theme_picker.xml

@@ -52,8 +52,8 @@
         android:layout_height="wrap_content"
         android:contentDescription="@string/onboarding_theme_light_title"
         android:elevation="1dp"
-        android:translationX="-7dp"
-        android:translationY="-8dp"
+        android:translationX="@dimen/onboarding_dual_pane_radio_button_translation_x"
+        android:translationY="@dimen/onboarding_dual_pane_radio_button_translation_y"
         app:layout_constraintStart_toStartOf="@+id/theme_light_image"
         app:layout_constraintTop_toTopOf="@+id/theme_light_image"
         app:onboardingKey="@string/pref_key_light_theme" />
@@ -64,7 +64,7 @@
         android:layout_height="wrap_content"
         android:layout_marginStart="16dp"
         android:layout_marginTop="16dp"
-        android:background="@drawable/onboarding_light_theme"
+        android:background="@drawable/ic_onboarding_light_theme"
         android:contentDescription="@string/onboarding_theme_light_title"
         android:foreground="@drawable/rounded_ripple"
         app:layout_constraintEnd_toStartOf="@+id/theme_dark_image"
@@ -78,8 +78,8 @@
         android:layout_height="wrap_content"
         android:contentDescription="@string/onboarding_theme_dark_title"
         android:elevation="1dp"
-        android:translationX="-7dp"
-        android:translationY="-8dp"
+        android:translationX="@dimen/onboarding_dual_pane_radio_button_translation_x"
+        android:translationY="@dimen/onboarding_dual_pane_radio_button_translation_y"
         app:layout_constraintStart_toStartOf="@+id/theme_dark_image"
         app:layout_constraintTop_toTopOf="@+id/theme_dark_image"
         app:onboardingKey="@string/pref_key_dark_theme" />
@@ -91,7 +91,7 @@
         android:layout_marginStart="16dp"
         android:layout_marginTop="16dp"
         android:layout_marginEnd="16dp"
-        android:background="@drawable/onboarding_dark_theme"
+        android:background="@drawable/ic_onboarding_dark_theme"
         android:contentDescription="@string/onboarding_theme_dark_title"
         android:foreground="@drawable/rounded_ripple"
         app:layout_constraintEnd_toEndOf="parent"

app/src/main/res/values-ldrtl/dimens.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<resources>
+    <!--  Onboarding  -->
+    <dimen name="onboarding_dual_pane_radio_button_translation_x">7dp</dimen>
+</resources>

app/src/main/res/values/dimens.xml

@@ -127,4 +127,8 @@
     <dimen name="share_header_text_size">12sp</dimen>
     <dimen name="share_progress_bar_margin">16dp</dimen>
 
+    <!--  Onboarding  -->
+    <dimen name="onboarding_dual_pane_radio_button_translation_x">-7dp</dimen>
+    <dimen name="onboarding_dual_pane_radio_button_translation_y">-8dp</dimen>
+
 </resources>