ci: add publiccode.yml validation workflow

Author: publiccode-pr-bot

.github/workflows/publiccode-yml-validation.yml

@@ -0,0 +1,12 @@
+name: publiccode.yml validation
+
+on: [pull_request, push]
+
+jobs:
+  publiccode_yml_validation:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: italia/publiccode-parser-action@v1
+        with:
+          publiccode: 'publiccode.yml'