Prepare for vNext (#6319)

Co-authored-by: elle-j <elle-j@users.noreply.github.com>

CHANGELOG.md

@@ -1,3 +1,25 @@
+## vNext (TBD)
+
+### Deprecations
+* None
+
+### Enhancements
+* None
+
+### Fixed
+* <How to hit and notice issue? what was the impact?> ([#????](https://github.com/realm/realm-js/issues/????), since v?.?.?)
+* None
+
+### Compatibility
+* React Native >= v0.71.4
+* Realm Studio v14.0.0.
+* File format: generates Realms with format v23 (reads and upgrades file format v5 or later for non-synced Realm, upgrades file format v10 or later for synced Realms).
+
+### Internal
+<!-- * Either mention core version or upgrade -->
+<!-- * Using Realm Core vX.Y.Z -->
+<!-- * Upgraded Realm Core from vX.Y.Z to vA.B.C -->
+
 ## 12.4.0 (2023-12-13)
 
 ### Enhancements