chore: further automate release process

We use `np` to orchestrate the publication of a module to NPM. One of the steps `np` performs is a commit to edit `package.json`'s `version`.

As we have branch protection enabled for `main`, we have to raise a PR to get this commit in. Automate this process in the release script as it's pretty boring!

This change assumes one has the GitHub CLI installed.

README.md

@@ -79,7 +79,7 @@ To release a new version, run `./script/release`. You will need to be logged in
 
 The script automatically prepares a [GitHub Release](https://docs.github.com/en/github/administering-a-repository/about-releases) and opens a pre-populated form in your browser. Please complete the GitHub Release creation manually.
 
-You will also need to manually checkout a new branch and open a PR containing version bump changes which are automatically committed during the release process.
+It will also automatically create a PR to edit `version` in [`package.json`](./package.json).
 
 ### A note about release numbers
 

script/release

@@ -9,6 +9,13 @@ DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 if npm whoami &>/dev/null; then
   rm -rf ./lib
   npm run release
+
+  # The default branch is protected.
+  # Raise a chore PR to bump `version` in `package.json`.
+  NEW_VERSION=$(git log -1 --pretty=%B)
+  git checkout -b "release-${NEW_VERSION}"
+  git push -u origin "release-${NEW_VERSION}"
+  gh pr create --title "chore: ${NEW_VERSION}" --body ""
 else
   echo "You are not logged into npm!"
   echo "  Run 'npm login' first!"