Improved artboard classes

[kunitoki]

This pull request introduces several significant changes to the examples/render/source/main.cpp and modules/yup_gui files, focusing on refactoring the Artboard class and related functionalities. The most important changes include the introduction of the ArtboardFile class, refactoring the Artboard class to use ArtboardFile, and adding new input handling methods.

Changes to Artboard and ArtboardFile:

• Introduced the ArtboardFile class to encapsulate the handling of artboard files, including methods for loading from files and streams.
• Refactored the Artboard class to use ArtboardFile instead of directly handling rive::File. This includes adding a constructor and setFile method that accept ArtboardFile.
• Removed old methods loadFromFile and loadFromStream from Artboard and replaced them with setFile and clear methods.

Input Handling Enhancements:

• Added new methods to the Artboard class for handling boolean, number, and trigger inputs, including hasBoolInput, setBoolInput, hasNumberInput, setNumberInput, hasTriggerInput, and triggerInput.
• Implemented methods to get and set all inputs, and to set individual inputs.