Replace extrafont with systemfonts

[edwardarchaeology]

Replace extrafont with systemfonts

Summary

This PR migrates the waffle package from the archived extrafont package to the actively maintained systemfonts package, resolving dependency on unmaintained software and fixing compatibility issues with modern ggplot2.

Motivation

• extrafont has been archived on CRAN and is no longer maintained
• Using an archived package poses long-term maintenance and compatibility risks
• systemfonts is actively maintained and is the recommended modern approach for font handling in R

Changes Made

Core Font Handling

• Replaced extrafont with systemfonts for all font detection and registration
• Updated load_fontawesome() to use systemfonts::register_font() instead of extrafont::font_import()
• Replaced extrafont::choose_font() with .has_font() helper using systemfonts::match_fonts()

Bug Fixes

• Fixed ggplot2 3.4.0+ deprecation: Changed size to linewidth in geom_tile() calls
• Fixed systemfonts 1.1.0+ deprecation: Changed match_font() to match_fonts()

Documentation Updates

• Removed all references to extrafont from documentation and examples
• Updated install_fa_fonts() with clear instructions for Windows users
• Added helpful warnings about font rendering on Windows graphics devices
• Updated all .Rd documentation files

Improved User Experience

• Better error messages that guide users to solutions
• Clearer font installation instructions, especially for Windows
• Added platform-specific guidance for graphics device compatibility

Files Modified

• DESCRIPTION: Updated dependency from extrafont to systemfonts (version bumped to 1.0.3)
• NAMESPACE: Updated imports
• R/waffle-package.R: Updated imports
• R/font-helpers.R: Created with .has_font() helper using systemfonts
• R/zzz.R: Rewrote load_fontawesome() for systemfonts
• R/waffle.R: Updated font checking, fixed deprecations, improved docs
• R/fontawesome.R: Enhanced install_fa_fonts() with detailed instructions
• man/install_fa_fonts.Rd: Updated documentation
• man/waffle.Rd: Updated documentation
• .gitignore: Added test files

Testing

• ✅ All basic waffle chart functionality works without changes
• ✅ Font Awesome glyph rendering works (with system-wide font installation on Windows)
• ✅ No breaking changes to user-facing API
• ✅ Backward compatible with existing code

Known Limitations

On Windows, graphics devices require system-wide font installation for Font Awesome glyphs (same as before, but now with clearer instructions). This is a Windows graphics device limitation, not a systemfonts issue.

Benefits

1. No dependency on archived/unmaintained package
2. Modern, actively maintained font handling
3. Better error messages and user guidance
4. Compatible with latest ggplot2 versions
5. Simpler implementation with fewer dependencies
6. Future-proof maintenance

Backward Compatibility

This change is fully backward compatible:

• All existing user code continues to work without modification
• Font Awesome glyph usage works the same way (with clearer setup instructions)
• No changes to function signatures or user-facing API

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Additional Notes:

• A detailed migration summary is included in MIGRATION_NOTES.md
• This resolves potential CRAN submission issues related to archived dependencies