Add content description for images and radio button

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

@@ -50,6 +50,7 @@
         android:id="@+id/theme_light_radio_button"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
+        android:contentDescription="@string/onboarding_theme_light_title"
         android:elevation="1dp"
         app:layout_constraintBottom_toBottomOf="@+id/theme_light_image"
         app:layout_constraintCircle="@id/theme_light_image"
@@ -67,6 +68,7 @@
         android:layout_marginStart="16dp"
         android:layout_marginTop="16dp"
         android:background="@drawable/onboarding_light_theme"
+        android:contentDescription="@string/onboarding_theme_light_title"
         android:foreground="@drawable/rounded_ripple"
         app:layout_constraintEnd_toStartOf="@+id/theme_dark_image"
         app:layout_constraintHorizontal_bias="0.5"
@@ -77,6 +79,7 @@
         android:id="@+id/theme_dark_radio_button"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
+        android:contentDescription="@string/onboarding_theme_dark_title"
         android:elevation="1dp"
         app:layout_constraintBottom_toBottomOf="@+id/theme_dark_image"
         app:layout_constraintCircle="@id/theme_dark_image"
@@ -94,6 +97,7 @@
         android:layout_marginTop="16dp"
         android:layout_marginEnd="16dp"
         android:background="@drawable/onboarding_dark_theme"
+        android:contentDescription="@string/onboarding_theme_dark_title"
         android:foreground="@drawable/rounded_ripple"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintHorizontal_bias="0.5"