Improve C89 compliance and code standards (#93)

* Add stb_image implementation file

This commit introduces the implementation of stb_image functions in a new source file, stb_image_impl.c. This file includes the necessary definitions to enable the functionality provided by the stb_image library. Only one C file should define STB_IMAGE_IMPLEMENTATION to avoid multiple definitions.

* Update binary libraries for various architectures

* feat: Implement in-game file browser for FreeIntv

- Added comprehensive technical overview and visual reference documentation for the file browser feature.
- Added support for various platforms, ensuring consistent behavior across Windows, Linux, macOS, Android, Switch, and Vita.
- Included error handling strategies and performance considerations for efficient operation.
- Updated build configurations to include new source files for different architectures (arm64-v8a, armeabi-v7a, riscv64, x86, x86_64).

* feat: Add initial libretro info file for FreeIntvTSOverlay

* Add object dependency files for FreeIntvTSOverlay source files

- Created dependency files for various source files including cart.c, controller.c, cp1610.c, and others.
- Updated dependencies for libretro-common components such as compat_posix_string.c, compat_snprintf.c, and file_path.c.
- Included necessary headers for each source file to ensure proper compilation.
- Enhanced project structure by organizing object files and their dependencies for better build management.

* feat: Update documentation and code for FreeIntvTSOverlay touchscreen support

* Enhance README with images and contributor details

Added images and updated contributors section in README.

* docs: Enhance README with details on touchscreen and mouse input for overlays

* Implement code changes to enhance functionality and improve performance

* Add Ko-fi username for funding

Added Ko-fi username for funding support.

* chore: Prepare for upcoming feature enhancements and optimizations

* chore: Update documentation for clarity and consistency

* Refactor code structure for improved readability and maintainability

* Checked compile on Android, Windows, and Linux

* Refactor code structure for improved readability and maintainability

* Implement feature X to enhance user experience and fix bug Y in module Z

* chore: Update README for clarity and consistency

* Fix: Revert valid_extensions from 'intv' to 'int' to restore ZIP file loading

* chore: Update .gitignore to exclude build artifacts and IDE files

* chore: Remove build artifacts tracked by git (now in .gitignore)

* refactor: Rename asset folder from FreeIntvTS_Overlays to freeIntv_image_assets

* Removed utility buttons and added logo banner, prepping for change to a 'core option'.

* Changed naming entries to FreeIntv without the TS Overlay to prepare for change to core option from separate core

* Incorporate PNG files into the code to alleviate need for external files

* corrected overlay loading code, and fixed keypad transparency

* updated documentation and screenshots

* Enhance user documentation with installation steps and dual-screen display instructions

* Update FreeIntv_libretro.info for improved clarity and accuracy in display name, supported extensions, and description

* Add dual-screen touchscreen and overlay support to FreeIntv core

- Implement side-by-side dual-screen rendering (1074×600 workspace)
- Add touchscreen hotspot input detection for 12 keypad buttons
- Support ROM-specific PNG overlays (370×600 pixels)
- Add cross-platform input handling (Android, Windows, Linux)
- Include screen swap functionality
- Update documentation with setup and usage instructions
- Update core metadata and info file
- Remove debug logging infrastructure
- Maintain full backward compatibility

* Update FreeIntv_libretro.info, README.md, and USER_GUIDE.md for enhanced onscreen interactive keypad overlays and improved versioning

* fix: Correct corename typo in FreeIntv_libretro.info

* Corrected multi-screen core option menu item.  Fixed onscreen keypad in default single screen mode.

* Updated wording for the new core option to specify restart and touchscreen/mouse are required.

* Add step to mark repo as safe in workflow

* Updated readme and user guide

* modified code to comply with c89 coding model

* Removed printf and fflush commands leftover from debugging code

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Co-authored-by: Jason Carr <[email protected]>

Author: jcarr71