[master] Update GitHub Actions (#331)

Copied from `https://github.com/knative/.github/tree/master/workflow-templates`.
/assign n3wscott vagababov
/cc n3wscott vagababov

.github/workflows/knative-style.yaml

@@ -60,3 +60,15 @@ jobs:
               exit 1
           fi
           echo "${{ github.repository }} is formatted correctly."
+
+      - id: golangci_configuration
+        uses: andstor/file-existence-action@v1
+        with:
+          files: .golangci.yaml
+
+      - name: Go Lint
+        if: steps.golangci_configuration.outputs.files_exists == 'true'
+        uses: golangci/golangci-lint-action@v2
+        with:
+          version: v1.30
+          only-new-issues: true # for initial defensiveness