docs: Add version check step to RELEASING.md

RELEASING.md

@@ -1,16 +1,18 @@
-1. Make sure to have an environment set up with `hatch` installed. See `CONTRIBUTING.md`.
+1. Check all [Vega project](https://github.com/orgs/vega/repositories?type=source) versions are up-to-date. See [NOTES_FOR_MAINTAINERS.md](NOTES_FOR_MAINTAINERS.md)
+
+2. Make sure to have an environment set up with `hatch` installed. See [CONTRIBUTING.md](CONTRIBUTING.md).
    Remove any existing environments managed by `hatch` so that it will create new ones
    with the latest dependencies when executing the commands further below:
 
         hatch env prune
 
-2. Make certain your branch is in sync with head, and that you have no uncommitted modifications. If you work on a fork, replace `origin` with `upstream`:
+3. Make certain your branch is in sync with head, and that you have no uncommitted modifications. If you work on a fork, replace `origin` with `upstream`:
 
         git checkout main
         git pull origin main
         git status  # Should show "nothing to commit, working tree clean"
 
-3. Do a clean doc build:
+4. Do a clean doc build:
 
         hatch run doc:clean-all
         hatch run doc:build-html
@@ -19,62 +21,62 @@
    Navigate to http://localhost:8000 and ensure it looks OK (particularly
    do a visual scan of the gallery thumbnails).
 
-4. Create a new release branch:
+5. Create a new release branch:
 
         git switch -c version_5.0.0
 
-5. Update version to, e.g. 5.0.0:
+6. Update version to, e.g. 5.0.0:
 
    - in ``altair/__init__.py``
    - in ``doc/conf.py``
 
-6. Commit changes and push:
+7. Commit changes and push:
 
         git add . -u
         git commit -m "chore: Bump version to 5.0.0"
         git push
 
-7. Merge release branch into main, make sure that all required checks pass
+8. Merge release branch into main, make sure that all required checks pass
 
-8. On main, build source & wheel distributions. If you work on a fork, replace `origin` with `upstream`:
+9.  On main, build source & wheel distributions. If you work on a fork, replace `origin` with `upstream`:
 
         git switch main
         git pull origin main
         hatch clean  # clean old builds & distributions
         hatch build  # create a source distribution and universal wheel
 
-9. publish to PyPI (Requires correct PyPI owner permissions):
+10. publish to PyPI (Requires correct PyPI owner permissions):
 
         hatch publish
 
-10. build and publish docs (Requires write-access to altair-viz/altair-viz.github.io):
+11. build and publish docs (Requires write-access to altair-viz/altair-viz.github.io):
 
         hatch run doc:publish-clean-build
 
-11. On main, tag the release. If you work on a fork, replace `origin` with `upstream`:
+12. On main, tag the release. If you work on a fork, replace `origin` with `upstream`:
 
        git tag -a v5.0.0 -m "Version 5.0.0 release"
        git push origin v5.0.0
 
-12. Create a new branch:
+13. Create a new branch:
 
        git switch -c maint_5.1.0dev
 
-13. Update version and add 'dev' suffix, e.g. 5.1.0dev:
+14. Update version and add 'dev' suffix, e.g. 5.1.0dev:
 
     - in ``altair/__init__.py``
     - in ``doc/conf.py``
 
-14. Commit changes and push:
+15. Commit changes and push:
 
         git add . -u
         git commit -m "chore: Bump version to 5.1.0dev"
         git push
         
-15. Merge maintenance branch into main
+16. Merge maintenance branch into main
 
-16. Double-check that a conda-forge pull request is generated from the updated
+17. Double-check that a conda-forge pull request is generated from the updated
     pip package by the conda-forge bot (may take up to several hours):
     https://github.com/conda-forge/altair-feedstock/pulls
 
-17. Publish a new release in https://github.com/vega/altair/releases/
+18. Publish a new release in https://github.com/vega/altair/releases/