MAINT: update changelog for v3.1
## Version 3.1.0 (unreleased)
+Update includes full compatibility with version 3.3 of Vega-Lite.
+
+
### Enhancements
+- Added support for [vega themes](https://github.com/vega/vega-themes) via
+ ``alt.themes.enable(theme_name)`` (#1539)
+
+- Added an ``alt.renderers.disable_max_rows()`` method for disabling the
+ maximum rows check (#1538)
+
+- Improved user-facing warnings/errors around layering and faceting (#1535).
+
- ``data`` argument is now properly handled by ``Chart.properties`` (#1525)
- Compound charts (layer, concat, hconcat, vconcat) now move data to the top
See ``altair/examples/us_population_over_time_facet.py`` for a more
complete example.
+### Bug fixes
+
+- Make ``chart.serve()`` and ``chart.save()`` respect the data transformer
+ setting (#1538)
+
+- Fixed a deserialization bug for certain chart specs in schemapi (#1543)
+
### Backward-Incompatible Changes
- ``alt.Chart.facet()`` now accepts a wrapped facet encoding as a first positional
