Build: Stop using ::set-output in GitHub Actions

The `set-output` workflow is deprecated in favor of using environment
variables, see:
https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Author: mgol

.github/workflows/test.yml

@@ -25,7 +25,7 @@ jobs:
       - name: Get npm cache directory
         id: npm-cache-dir
         run: |
-          echo "::set-output name=dir::$(npm config get cache)"
+          echo "dir=\"$(npm config get cache)\"" >> $GITHUB_OUTPUT
 
       - name: Cache npm dependencies
         uses: actions/cache@v3