Revise release notes for version 1.9.0

Updated release notes for version 1.9.0 to reflect changes in data types and the addition of MeaningsTable and BaseDynamicTable.

Author: rly

docs/source/hdmf_common_release_notes.rst

@@ -5,13 +5,16 @@ hdmf-common Release Notes
 
 1.9.0 (Upcoming)
 ----------------------
-- Changed the dtype of `ElementIdentifiers` and `DynamicTableRegion` from "int" to "int32". Under HDMF
+- Changed the dtype of ``ElementIdentifiers`` and ``DynamicTableRegion`` from "int" to "int32". Under HDMF
   schema language 2.x, "int" means "int32" so this change has no functional impact, except when displaying the
   spec, such as in error messages.
-- Added `MeaningsTable`, a table for storing meanings for values in linked `VectorData` objects.
-  This is useful for annotating categorical data stored in a `DynamicTable`. Added a group named "meanings_tables"
-  to `DynamicTable` to hold `MeaningsTable` objects that provide meanings for `VectorData` columns in the
-  `DynamicTable`.
+- Added ``MeaningsTable``, a table for storing meanings for values in linked ``VectorData`` objects.
+  This is useful for annotating categorical data stored in a ``DynamicTable``. Added a group named "meanings_tables"
+  to ``DynamicTable`` to hold ``MeaningsTable`` objects that provide meanings for ``VectorData`` columns in the
+  ``DynamicTable``.
+- Created a new type ``BaseDynamicTable`` that does not have a group of ``MeaningsTable`` objects, and refactored
+  ``DynamicTable`` to move non-MeaningsTable specifications to ``BaseDynamicTable`` and have ``DynamicTable``
+  extend ``BaseDynamicTable``.
 - Minor changes to data type docstrings to improve clarity.
 
 1.8.0 (August 4, 2023)