Merge "Add a README to frameworks/base/config." am: ec2aafa614 am: 846984a499 am: 2616a44c26 am: 72da11e20b

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1885634

Change-Id: Idf4d2813c845e62b3273c10bf948632419c21ca3