Fix for issue with checkZFT static method

[kalwalt]

This pull request includes several changes aimed at improving code quality and updating dependencies. The most important changes involve refactoring variable declarations, removing unnecessary console logs, updating the TypeScript version, and modifying a utility function.

Code Quality Improvements:

• Refactored variable declarations from var to let and const in js/artoolkitNFT.embed_ES6_worker.js and js/artoolkitNFT.multi_worker.js to improve scope handling and code readability. [1] [2]
• Removed unnecessary console.log statements in js/artoolkitNFT.embed_ES6_worker.js and js/artoolkitNFT_ES6.worker.js to clean up the console output. [1] [2]

Dependency Updates:

• Updated the TypeScript version in package.json from 5.5.4 to 5.6.3 to ensure compatibility with the latest features and bug fixes.

Utility Function Modification:

• Updated the checkZFT function in src/Utils.ts to use synchronous XMLHttpRequest instead of axios, simplifying the function and ensuring correct return types.

Configuration Changes:

• Removed the Node.js language specification from .travis.yml as it is no longer needed.This pull request includes a significant change to the checkZFT method in the Utils class within the src/Utils.ts file. The method has been refactored to simplify its implementation and improve its reliability, and to solve an issue while loading not .zft files

Key changes:

• Simplified the checkZFT method to use a synchronous XMLHttpRequest instead of an asynchronous axios request. This change ensures that the method returns a boolean value directly based on the HTTP response status.