Release v0.9.0 (tendermint#99)

* Prepare changelog

Signed-off-by: Thane Thomson <connect@thanethomson.com>

* Fix date in changelog summary

Signed-off-by: Thane Thomson <connect@thanethomson.com>

* Update CHANGELOG.md

Co-authored-by: Andy Nogueira <me@andynogueira.dev>

---------

Signed-off-by: Thane Thomson <connect@thanethomson.com>
Co-authored-by: Andy Nogueira <me@andynogueira.dev>

.changelog/v0.9.0/summary.md

@@ -0,0 +1,6 @@
+*December 1, 2023*
+
+This release primarily updates some key dependencies, including adding support
+for RocksDB v8. It also bumps the minimum Go version to v1.21 in order for
+CometBFT to be able to use it in the E2E testing framework for the latest major
+releases.

CHANGELOG.md

@@ -1,5 +1,24 @@
 # CHANGELOG
 
+## v0.9.0
+
+*December 1, 2023*
+
+This release primarily updates some key dependencies, including adding support
+for RocksDB v8. It also bumps the minimum Go version to v1.21 in order for
+CometBFT to be able to use it in the E2E testing framework for the latest major
+releases.
+
+### DEPENDENCIES
+
+- Use RocksDB v8, testing with v8.8.1
+  ([\#97](https://github.com/cometbft/cometbft-db/pull/97))
+
+### GO VERSION
+
+- Bump minimum Go version to v1.21
+  ([\#98](https://github.com/cometbft/cometbft-db/pull/98))
+
 ## v0.8.0
 
 *Apr 26, 2023*