nit

Missed out this comment to notify that it's available on only pre-release v2.3.9-0 version.

Author: shahbaz17

docs/sdk/core-kit/mpc-core-kit/usage.mdx

@@ -65,6 +65,9 @@ indexes. Using this function you can add multi-address account support to your a
 
 As an application, you need to persist this account index in the application state.
 
+This feature is still in [pre-release](https://github.com/Web3Auth/mpc-core-kit/releases/tag/v2.3.0-0), so there can be some **breaking changes in
+upcoming versions.**
+
 :::
 
 #### Usage