[My WordPress] Adding Portuguese translation for about page and Welcome page

[fellyph]

This pull request adds Brazilian Portuguese (pt_BR) localization support to the My WordPress plugin and introduces the initial Portuguese content files. The main changes include updating the translations configuration to recognize the new language, setting up fallbacks for other Portuguese dialects, and providing localized content for the about page and welcome post.

Localization support:

• Added pt_BR (Brazilian Portuguese) to the languages section in translations.json, mapping it to the pt content directory.
• Set up fallbacks in translations.json so that pt_PT, pt_AO, and pt_MZ all use the pt_BR content.

Steps to test

1. Pull the branch locally
2. Run the blueprints located at blueprints/my-wordpress/blueprint.json with the locale set to Portuguese
3. Check the translation on the page