Add internationalization support with astro-i18next integration

- Implemented astro-i18next for multi-language support, including English, Dutch, and Italian.
- Configured default locale and language fallback settings.
- Defined routes for localized content in the configuration.
- Updated package.json and package-lock.json to include new dependencies for i18next and related plugins.

node_modules/iso-639-1/.travis.yml

@@ -0,0 +1,6 @@
+language: node_js
+node_js:
+    - '8.0'
+    - '6.1'
+script:
+    - npm run test