Merge "[sf] Add readme for surfaceflinger frontend" into udc-dev am:...

Merge "[sf] Add readme for surfaceflinger frontend" into udc-dev am: 0f0d7b03 am: 7a66ef37 am: 1a6b6fca am: 0b5ef69a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/native/+/23272393



Change-Id: If3efb69700b7e31cc5925f47c9f52a1c90beaf8f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>