feat: add Catalan (ca) and Spanish (es) translations

[Rabosa616]

Description

Add complete Catalan (ca) and Spanish (es) translations for the Universal Notifier integration, including UI translation files, full README translations, and User Guide translations.

New files:

• custom_components/universal_notifier/translations/ca.json — Catalan UI strings
• custom_components/universal_notifier/translations/es.json — Spanish UI strings
• README_CA.md — Full Catalan README
• README_ES.md — Full Spanish README
• USER_GUIDE_CA.md — Full Catalan User Guide
• USER_GUIDE_ES.md — Full Spanish User Guide

Modified files:

• README.md — Added a translations table with links to all language versions

Motivation and Context

The integration currently only supports English and Italian. Adding Catalan and Spanish translations improves accessibility for a wider user base, particularly in Spain where both languages are widely
spoken.

How has this been tested?

• Verified that both JSON files are valid and parseable
• Confirmed that all keys match the structure of the existing en.json and it.json files
• README and User Guide files follow the same structure as the English and Italian originals

Screenshots (if appropriate):

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[jumping2000]

hello I release a test version with your changes, I hope I will have time to solve other minor issues and make a prod version. Thanks