replace publishing of the test object with actual docusaurus build

I've used `sync` instead of `cp`, because it only does the copying,
when file doesn't exist yet or wasn't modified.
The `--delete` flag also takes care of deleting files that are not present anymore.

Author: MarianKijewski

.github/workflows/publish.yaml

@@ -35,10 +35,12 @@ jobs:
         uses: actions/setup-node@v3
         with:
           node-version: '20'
-      - name: Publish test object to S3
-        run: |
-          echo "<h1>This is a test file generated by ${{ github.workflow }}-${{ github.run_id}}</h1>" > test.html
-          aws s3 cp test.html s3://$S3_BUCKET_NAME/test.html
+      - name: Install dependencies
+        run: npm ci
+      - name: Build Docusaurus site
+        run: npm run build
+      - name: Sync build artifacts to S3
+        run: aws s3 sync ./build/ s3://$S3_BUCKET_NAME --delete
       - name: Invalidate CloudFront Cache
         run: |
           aws cloudfront create-invalidation --distribution-id ${CF_DISTRIBUTION_ID} --paths "/*"