New tokens arquitecture POC

[GomezIvann]

Checklist

• The build process is done without errors. All tests pass in the /lib directory.
• Self-reviewed the code before submitting.
• Meets accessibility standards.
• Added/updated documentation to /website as needed.
• Added/updated tests as needed.

Purpose
A test for the new tokens architecture.

Description
This PR includes:

• New CSS files for global styling: fonts.css and tokens.css.
• inyectStyles flag for default styling within the library build.
• New exported function setCustomTheme (provisional name) for application-level theming (only once intented per application).
• New exported provider HalstackThemeProvider (provisional name) for dynamic and specific theming strategies.
• Button code page example.