hash verification for datasets used in vision transformer and neuralchat finetuning workflow interface examples

[kta-intel]

Details:
Adding hash verification steps in the Vision Transformer and NeuralChat Finetuning workflow interface examples

• for vision transformer, used openfl.utilities.validate_file_hash
• for neuralchat, creating custom hash validation function with a hash.txt file because it was to validate multiple files (though in retrospect, could have just ran a loop with validate_file_hash instead, let me know the preference)

Additional minor change

• for neuralchat example, removed cell for installing ITREX and neuralchat dependencies in favor of linking to repository installation guide. easier for a user to stay up to date on dependencies this way, especially if the notebook installs the latest openfl and workflow interface requirements