Validate plugin manifests in CI

.github/workflows/ci.yml

@@ -0,0 +1,33 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    timeout-minutes: 2
+    steps:
+      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0
+        with:
+          persist-credentials: false
+      - name: Validate JSON manifests
+        run: |
+          python3 - <<'PY'
+          import json
+          import subprocess
+          from pathlib import Path
+
+          names = subprocess.check_output(["git", "ls-files", "-z", "--", "*.json"])
+          for name in filter(None, names.split(b"\0")):
+              path = Path(name.decode("utf-8"))
+              if path.is_symlink() or not path.is_file():
+                  raise ValueError(f"manifest must be a regular file: {path}")
+              json.loads(path.read_text(encoding="utf-8"))
+              print(f"valid: {path}")
+          PY