feat: add internationalization section to PR template

Add i18n section to remind contributors to consider localized content updates when modifying main docs. Main docs support French Canadian (fr-ca/) and Japanese (ja-jp/) locales.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: btiernay

.github/pull_request_template.md

@@ -49,6 +49,15 @@ If redirects are needed, please add them to the `redirects` array in the appropr
 }
 ```
 
+## 🌍 Internationalization
+
+**Localized content (main docs only):**
+- [ ] Not applicable - no English content changes
+- [ ] Changes apply to English content only (localized versions will be updated separately)
+- [ ] Changes include updates to localized versions (`fr-ca/`, `ja-jp/`)
+
+**Note:** Main docs support French Canadian (`main/docs/fr-ca/`) and Japanese (`main/docs/ja-jp/`). If you're updating existing pages, consider whether localized versions need corresponding updates.
+
 ## 📊 Impact
 
 **User-facing changes:**