Add black/whitelist support

[LightArrowsEXE]

Hello, thanks for creating this package!

A feature I'm missing is the ability to blacklist certain characters (seeing as tesseract keeps catching I as |). Scouring through the code, I could not find any options for this. Having the ability to pass a string of disallowed characters would be nice.

Similarly, whitelist supports would also be welcome for similar reasons. However if only one or the other can be supported, I think it's best to support blacklists instead (or to at least prioritise it if both are passed).

If there's currently no development time being put into this for a little while, I can also try to create a PR if you'd like me to.

Thanks again!