SDK only: add documentation tags.
SDK only: add documentation tags.

Also fix up the new support API demo documentation.

Change-Id: I7a6945ffafa6a93cd394d5ce5729d6f9dfc0a183

aosp-mirror/platform_frameworks_support,AndroidX/androidx,androidx/androidx,aosp-mirror/platform_frameworks_support,androidx/androidx,androidx/androidx,androidx/androidx,aosp-mirror/platform_frameworks_support,AndroidX/androidx,AndroidX/androidx,aosp-mirror/platform_frameworks_support,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,aosp-mirror/platform_frameworks_support