Add changelog for v1.0.0-alpha.16 (#2680)

* add changelog for v1.0.0-alpha.16

* update the changelog

* do some minor changes

CHANGELOG.md

@@ -4,6 +4,43 @@ All notable changes to Zebra will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org).
 
+## [Zebra 1.0.0-alpha.16](https://github.com/ZcashFoundation/zebra/releases/tag/v1.0.0-alpha.16) - 2021-08-27
+
+Zebra's latest alpha finishes most of the state work needed for NU5 testnet activation and starts the mempool work.
+
+### Added
+
+#### Network Upgrade 5
+
+- Finished ZIP-209: Prohibit Negative Shielded Chain Value Pool Balances (#2599, #2649, #2656, #2648, #2644)
+- ZIP-221 and ZIP-244: Commitment validation in non-finalized state and checkpoint verifier (#2609, #2633)
+- Orchard binding_verification_key support (#2441)
+
+#### Mempool
+
+- Mempool component, storage and errors (#2615, #2651)
+- Create a transaction crawler for the mempool (#2646, #2672)
+- Create and use types for unmined transactions and their IDs (#2634, #2666)
+- ZIP-239: Implement mempool transaction v5 data structures and network messages (#2618, #2638)
+- Return a transaction verifier from `zebra_consensus::init` (#2665)
+- Provide recent syncer response lengths as a watch channel (#2602)
+- Derive Copy and Clone for zebra-consensus errors (#2664)
+- ChainTip trait creation and usage (#2677, #2676)
+
+#### Metrics
+
+- Add a network message to the grafana dashboard (#2673)
+
+##### Documentation
+
+- Refactor Zebra metrics docs (#2678, #2687)
+
+### Fixed
+
+- Stop converting `Message::Inv(TxId+)` into `Request::TransactionsById` (#2660)
+- Fixed test.yml (#2635)
+- Fixed a clippy lint (#2642)
+
 ## [Zebra 1.0.0-alpha.15](https://github.com/ZcashFoundation/zebra/releases/tag/v1.0.0-alpha.15) - 2021-08-16
 
 Zebra's latest alpha contains the last of the changes to zebra chain state ahead of NU5 testnet activation and before concentrating on mempool work. The remaining NU5 validation will be completed prior to NU5 mainnet activation.