bump version to 0.9.0

because of new symlink functionality (even if a small change)

src/tufup/__init__.py

@@ -5,7 +5,7 @@
 
 # https://packaging.python.org/en/latest/guides/single-sourcing-package-version/
 # https://semver.org/
-__version__ = '0.8.1'
+__version__ = '0.9.0'
 
 logger = logging.getLogger(__name__)