ci: Use GITHUB_OUTPUT envvar instead of set-output command (#181)

`save-state` and `set-output` commands used in GitHub Actions are deprecated and [GitHub recommends using environment files](https://github.blog/changelog/2023-07-24-github-actions-update-on-save-state-and-set-output-commands/).

This PR updates the usage of `::set-output` to `"$GITHUB_OUTPUT"`

Instructions for envvar usage from GitHub docs:

https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
     steps:
       - name: Create URL to the run output
         id: vars
-        run: echo ::set-output name=run-url::https://github.com/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID
+        run: echo run-url=https://github.com/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID >> "$GITHUB_OUTPUT"
       - name: Update with Result
         uses: peter-evans/create-or-update-comment@v1
         with: