Bump package version to 0.2.9

Update pyproject.toml to set mdmodels_core version from 0.2.8 to 0.2.9 for a new patch release.

Author: JR-1991

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "maturin"
 
 [project]
 name = "mdmodels_core"
-version = "0.2.8"
+version = "0.2.9"
 description = "A tool to generate models, code and schemas from markdown files"
 requires-python = ">=3.8"
 classifiers = [