MNT: Prepare for next release

Author: QuLogic

Diff for: mpl_sphinx_theme/_version.py

@@ -4,5 +4,5 @@
 # Copyright (c) Matplotlib developers.
 # Distributed under the terms of the Modified BSD License.
 
-version_info = (3, 9, 0)
-__version__ = ".".join(map(str, version_info))
+version_info = (3, 9, 1)
+__version__ = ".".join(map(str, version_info)) + "dev0"