chore: add Open VSX Registry publishing step to workflow

Author: jrandolf

.github/workflows/publish.yaml

@@ -13,6 +13,10 @@ jobs:
         with:
           node-version: 20
       - run: npm ci
+      - name: Publish to Open VSX Registry
+        uses: HaaLeo/publish-vscode-extension@v2
+        with:
+          pat: ${{ secrets.OPEN_VSX_TOKEN }}
       - name: Publish to Visual Studio Marketplace
         uses: HaaLeo/publish-vscode-extension@v1
         with: