update github actions

Signed-off-by: Benny Samir Hierl <bennysamir@posteo.de>

.github/workflows/validation.yml

@@ -1,6 +1,9 @@
-name: ci
+name: validation
 
-on: [push]
+  pull_request:
+  push:
+    branches:
+      - main
 
 jobs:
   lint:
@@ -9,6 +12,8 @@ jobs:
       - uses: actions/checkout@v2
       - name: Set up NodeJs
         uses: actions/setup-node@v2
+        with:
+          node-version: 16
       - name: Install dependencies
         run: npm ci
       - name: Linter