feat(i18n): add internationalization support

This commit introduces internationalization (i18n) support by integrating the `@nuxtjs/i18n` module. It configures English (en) and
Simplified Chinese (zh-CN) locales, adds a language selector to the header, and internationalizes the index page content using
translation files.

.repomixignore

@@ -0,0 +1,4 @@
+# Add patterns to ignore here, one per line
+# Example:
+# *.log
+# tmp/