Set context for files in the com.android.bootanimation apex

Set the bootanim_file context for files in the com.android.boootanim
apex-module.

Bug: 116821733
Test: Verify that the new boot animation is used from next boot
Change-Id: I15e7b00bb8044eee550a4490a271b05ae14587b6
diff --git a/apex/com.android.bootanimation-file_contexts b/apex/com.android.bootanimation-file_contexts
new file mode 100644
index 0000000..83b4b58
--- /dev/null
+++ b/apex/com.android.bootanimation-file_contexts
@@ -0,0 +1 @@
+(/.*)?                   u:object_r:system_file:s0