Fix GitHub action syntax

Author: jack5github

.github/workflows/publish.yml

@@ -1,14 +1,20 @@
-- if: github.ref == 'refs/heads/main'
-  name: Publish to Visual Studio Marketplace
-  uses: HaaLeo/publish-vscode-extension@v2
-  with:
-    pat: ${{ secrets.VS_MARKETPLACE_TOKEN }}
-    registryUrl: https://marketplace.visualstudio.com
-  id: vsmPublish
-# TODO: Publish to Open VSX Registry
-# - if: github.ref == 'refs/heads/main'
-#   name: Publish to Open VSX Registry
-#   uses: HaaLeo/publish-vscode-extension@v2
-#   with:
-#     pat: ${{ secrets.OPEN_VSX_REGISTRY_TOKEN }}
-#     extensionFile: ${{ steps.vsmPublish.outputs.vsixPath }}
+on:
+  push:
+    branches:
+      - main
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Publish to Visual Studio Marketplace
+        uses: HaaLeo/publish-vscode-extension@v2
+        with:
+          pat: ${{ secrets.VS_MARKETPLACE_TOKEN }}
+          registryUrl: https://marketplace.visualstudio.com
+        id: vsmPublish
+      # TODO: Publish to Open VSX Registry
+      # - name: Publish to Open VSX Registry
+      #   uses: HaaLeo/publish-vscode-extension@v2
+      #   with:
+      #     pat: ${{ secrets.OPEN_VSX_REGISTRY_TOKEN }}
+      #     extensionFile: ${{ steps.vsmPublish.outputs.vsixPath }}