Add v26 migrate docs (#1863)

* add migrate docs

* change date to TDB

CHANGELOG.md

@@ -36,6 +36,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ## [Unreleased]
 
+## [v0.26.0]
+
 ### Features
 - (precisebank) [#1906] Add new `x/precisebank` module with bank decimal extension for EVM usage.
 - (cli) [#1922] Add `iavlviewer` CLI command for low-level iavl db debugging.

migrate/v0_26/migrate.md

@@ -0,0 +1,77 @@
+# Kava 16 Upgrade Instructions
+
+## Software Version and Key Dates
+
+- The version of `kava` for Kava 16 is `v0.26.0`
+- The Kava 16 chain will be shutdown with a `SoftwareUpgradeProposal` that
+  activates at approximately 15:00 UTC on TBD, 2024.
+
+## Dependency Changes
+
+## API Changes
+
+If you are a consumers of the legacy REST API known as the LCD, please note that this has been deprecated as a part of cosmos-sdk v47. [Additional details can be found here.](./legacy_rest.md)
+
+### For validators using RocksDB
+
+> [!NOTE]
+> If you use goleveldb or other database backends, this is not required.
+
+If you use RocksDB as your database backend, you will need to update RocksDB if you are using `<= v8.1.1`. The tested and recommended RocksDB version is `v8.10.0`.
+Please reference the [RocksDB repository](https://github.com/facebook/rocksdb/tree/v8.10.0) to update your installation before building the RocksDB kava binary.
+
+### On the day of the upgrade
+
+The kava chain is expected to halt at block height **xxx**. **Do not stop your node and begin the upgrade before the upgrade height**, or you may go offline and be unable to recover until after the upgrade!
+
+**Make sure the kava process is stopped before proceeding and that you have backed up your validator**. Failure to backup your validator could make it impossible to restart your node if the upgrade fails.
+
+**Ensure you are using golang 1.21.x and not a different version.** Golang 1.20 and below may cause app hash mismatches!
+
+To update to v0.26.0
+
+```sh
+# check go version - look for 1.21!
+go version
+# go version go1.21.6 linux/amd64
+
+# in the `kava` folder
+git fetch
+git checkout v0.26.0
+
+# Note: Golang 1.21 must be installed before this step
+make install
+
+# verify versions
+kava version --long
+# name: kava
+# server_name: kava
+# version: 0.26.0
+# commit: <commit placeholder>
+# build_tags: netgo ledger,
+# go: go version go1.21.6 linux/amd64
+# build_deps:
+#  ...
+# cosmos_sdk_version: v0.47.10
+
+# Restart node -
+kava start
+```
+
+### Risks
+
+As a validator, performing the upgrade procedure on your consensus nodes carries a heightened risk of double-signing and being slashed. The most important piece of this procedure is verifying your software version and genesis file hash before starting your validator and signing.
+
+The riskiest thing a validator can do is discover that they made a mistake and repeat the upgrade procedure again during the network startup. If you discover a mistake in the process, the best thing to do is wait for the network to start before correcting it. If the network is halted and you have started with a different genesis file than the expected one, seek advice from a Kava developer before resetting your validator.
+
+### Recovery
+
+Prior to applying the Kava 16 upgrade, validators are encouraged to take a full data snapshot at the upgrade height before proceeding. Snap-shotting depends heavily on infrastructure, but generally this can be done by backing up the .kava directory.
+
+It is critically important to back-up the .kava/data/priv_validator_state.json file after stopping your kava process. This file is updated every block as your validator participates in consensus rounds. It is a critical file needed to prevent double-signing, in case the upgrade fails and the previous chain needs to be restarted.
+
+In the event that the upgrade does not succeed, validators and operators must downgrade back to v0.25.x of the Kava software and restore to their latest snapshot before restarting their nodes.
+
+### Coordination
+
+If the Kava 16 chain does not launch by TBD at 00:00 UTC, the launch should be considered a failure. In the event of launch failure, coordination will occur in the [Kava discord](https://discord.com/invite/kQzh3Uv).