Add a stub for v23 migration doc

dmkozh · dmkozh · commit 44baf28bc3cf · 2025-05-19T20:26:46.000-04:00
diff --git a/soroban-sdk/src/_migrating.rs b/soroban-sdk/src/_migrating.rs
@@ -1,3 +1,6 @@
+//! # Migrating from v22 to v23
+//! TBD
+//! 
 //! # Migrating from v21 to v22
 //!
 //! 1. [`Env::register`] and [`Env::register_at`] replace [`Env::register_contract`] and [`Env::register_contract_wasm`].
