Add Vala LINT

.github/workflows/valalint.yml

@@ -0,0 +1,23 @@
+name: CI
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+
+    container:
+      image: valalang/lint
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Lint
+        run: io.elementary.vala-lint -d .