Add Multilingual Build Support

[iksnae]

Multilingual Support Enhancements

This pull request adds proper support for building and releasing the Spanish translation of the book.

Changes Made

1. Updated Build Script

   • Added support for building different language versions of the book
   • Created a language array to easily add more languages in the future
   • Generates properly named output files for each language

2. Updated GitHub Workflow

   • Now includes Spanish PDF, EPUB, and MOBI files in the release
   • Organizes the release notes with separate sections for each language
   • Adds links to both English and Spanish web versions

3. HTML Webpages

   • Added Spanish HTML output in /es/ subdirectory
   • Main index.html file is still created from the English version
   • Spanish web version is accessible at https://iksnae.github.io/actual-intelligence/es/

How to Test

These changes can be tested locally by running the build script:

./build.sh

The script will now build both English and Spanish versions of the book.

Additional Notes

• The README.md has already been updated in a previous commit to include Spanish download links
• This change makes it easy to add more languages in the future by simply adding them to the language arrays

Looking forward to your feedback!