ci: add json syntax error check (#15)

Author: twishabansal

.github/workflows/json-lint.yml

@@ -0,0 +1,29 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Lint JSON
+
+on:
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  json-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+
+      - name: Run JSON Lint
+        run: jq . gemini-extension.json