REL: set version to 0.5.0

Author: lucascolley

RELEASING.md

@@ -1,5 +1,5 @@
 1. Update the version in `src/array_api_extra/__init__.py`
-2. Update the lockfile with `pixi update`
+2. Update the lockfile with `pixi update` and `pixi install`
 3. Push your changes
 4. Cut a release via the GitHub GUI
 5. Update the version to `{next micro version}.dev0`