[ci] add JSON validation CI workflow (#5837)

## Summary

Added GitHub Actions workflow and shell script to validate JSON syntax
in repository files, as in the past we have committed locales files with
invalid JSON.

## Changes

- **What**: Added CI workflow for JSON validation with `jq` syntax
checking
- **Dependencies**: CI workflow requires `jq` (pre-installed on
ubuntu-latest runners)

## Review Focus

Script exclusion patterns for TSConfig files and environment variable
override mechanism (`JSON_LINT_EXCLUDES`).

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5837-ci-add-JSON-validation-CI-workflow-27c6d73d365081a199b1d9ae9e4edfa4)
by [Unito](https://www.unito.io)

.github/workflows/json-validate.yaml

@@ -0,0 +1,15 @@
+name: Validate JSON
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  json-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Validate JSON syntax
+        run: ./scripts/cicd/check-json.sh