ci: lint JSON files using ESLint

Add GitHub Actions CI which lints json files
using official ESLint json plugin.

Signed-off-by: Yanase Yuki <dev@zpc.st>

eslint.config.mjs

@@ -0,0 +1,13 @@
+import { defineConfig } from "eslint/config";
+import json from "@eslint/json";
+
+export default defineConfig([
+	{
+		files: ["**/*.json"],
+		ignores: ["package-lock.json"],
+		plugins: { json },
+		language: "json/json",
+		extends: ["json/recommended"],
+	},
+]);
+