`tokenizer` should return `Result<Vec<Token>>` instead of `Vec<Token>`

[momeemt]

The tokenizer is currently implemented to return values of type Vec<Token>. However, tokenization can fail, and in such cases, it would be more appropriate for the function to return a Result<Vec<Token>, Error> to properly handle potential errors.

[momeemt]

I don't understand whether a tokenizer can throw an error.

[momeemt]

rel: #45