New changelog section to prepare for vNext

CHANGELOG.md

@@ -1,3 +1,26 @@
+# NEXT RELEASE
+
+### Enhancements
+* <New feature description> (PR [#????](https://github.com/realm/realm-core/pull/????))
+* None.
+
+### Fixed
+* <How do the end-user experience this issue? what was the impact?> ([#????](https://github.com/realm/realm-core/issues/????), since v?.?.?)
+* None.
+
+### Breaking changes
+* None.
+
+### Compatibility
+* Fileformat: Generates files with format v24. Reads and automatically upgrade from fileformat v10. If you want to upgrade from an earlier file format version you will have to use RealmCore v13.x.y or earlier.
+
+-----------
+
+### Internals
+* None.
+
+----------------------------------------------
+
 # 20.1.0 Release notes
 
 ### Enhancements