Add initial explanation of pinned blobs

README.md

@@ -24,6 +24,31 @@ Build inline with Android
 1. Sync this repo to $GAPPS_PATH where $GAPPS_PATH is the path to this repo
 2. Include $GAPPS_PATH/$ARCH/$ARCH-vendor.mk where $ARCH is arm, arm64, or x86 depending on the device's architecture
 
+Explanation of pinned blobs
+-------------------
+NOTE: All arch specific blobs not specifically explained here are pinned for the sake of being able to extract independently of the architecture of the source device.
+
+AndroidMigratePrebuilt.apk
+- This is from a marlin factory image to avoid crashes with the one found in the walleye factory images.
+
+GoogleCalendarSyncAdapter.apk
+- This is no longer included in Google system images and is required for syncing Google Calendar accounts with AOSP Calendar.
+
+PrebuiltExchange3Google.apk
+- This is no longer included in Google system images and is required for using Exchange accounts in the Gmail app.
+
+PrebuiltGmsCore.apk
+- This is a nodpi apk so that it works properly on all devices and updates to the appropriate one. This is generally from APKMirror and is not usually updated between major version updates.
+
+SetupWizard.apk
+- This is a non-pixel SetupWizard for better UX and less pixel-specific references.
+
+default-permissions.xml and privapp-permissions-google.xml
+- These do not always contain all the necessary permissions for apks which are not from the corresponding factory image, so they must be modified to avoid permission related crashes.
+
+libjni_latinimegoogle.so
+- This lib is no longer included in Google system images and is required for swype typing with AOSP LatinIME.
+
 Thanks and Credits
 -------------------