.github/workflows: add golangci-lint GH action (projectcontour#2976)

Uses https://github.com/marketplace/actions/run-golangci-lint to lint
code for new changes on PRs.

Fixes projectcontour#2972

Signed-off-by: Shayegan Hooshyari <sh.hooshyari@gmail.com>

.github/workflows/prbuild.yaml

@@ -49,13 +49,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-go@v2
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v2
         with:
-          go-version: '1.15.2'
-      - name: lint
-        run: |
-          go mod vendor
-          make lint
+          version: v1.31
+          only-new-issues: true
   codegen:
     runs-on: ubuntu-latest
     steps: