.github/workflows: run fmt and lint in CI

.github/workflows/ci.yaml

@@ -20,6 +20,18 @@ jobs:
       with:
         go-version: ${{ env.golang-version }}
     - run: make --always-make generate && git diff --exit-code
+  lint:
+    runs-on: ubuntu-latest
+    name: Jsonnet linter
+    steps:
+    - uses: actions/checkout@v2
+    - run: make --always-make lint
+  fmt:
+    runs-on: ubuntu-latest
+    name: Jsonnet formatter
+    steps:
+    - uses: actions/checkout@v2
+    - run: make --always-make fmt && git diff --exit-code
   unit-tests:
     runs-on: ubuntu-latest
     name: Unit tests