Add jest tests and CI workflow

__tests__/loadConfig.test.js

@@ -0,0 +1,13 @@
+const fs = require('fs');
+const path = require('path');
+const loadConfig = require('../src/config/loadConfig');
+
+test('loads configuration and merges defaults', () => {
+  const dir = fs.mkdtempSync(path.join(__dirname, 'cfg-'));
+  const file = path.join(dir, 'config.yaml');
+  fs.writeFileSync(file, 'site:\n  title: Test Site\n');
+  const cfg = loadConfig(file);
+  expect(cfg.site.title).toBe('Test Site');
+  expect(cfg.navigation.search).toBe(true);
+  fs.rmSync(dir, { recursive: true, force: true });
+});