maint: bump version to 0.4.dev0 in main branch (#344)

Author: clatapie

pyproject.toml

@@ -5,7 +5,7 @@ build-backend = "flit_core.buildapi"
 [project]
 # Check https://flit.readthedocs.io/en/latest/pyproject_toml.html for all available sections
 name = "pyconverter-xml2py"
-version = "0.3.dev0"
+version = "0.4.dev0"
 description = "PyConverter-XML2Py converter."
 readme = "README.rst"
 requires-python = ">=3.10,<4"