Add archive notice (#124)

Updare readme with archive notice.

Relates to:
* sei-protocol/sei-chain#2457

Author: masih

README.md

@@ -1,3 +1,7 @@
+
+> [!IMPORTANT]
+> This repository has been archived and is moved to [`sei-chain`](https://github.com/sei-protocol/sei-chain) as a nested module.
+
 # SeiDB
 SeiDB is the next-gen on-chain database which is designed to replace the [IAVL Store](https://github.com/cosmos/iavl) of Cosmos based chain.
 The goal of SeiDB is to improve the overall data access performance and prevent state bloat issues.