Allow negation ! for --ignore

[woodconn]

Your documentation shows how ignore can handle multiple file paths
https://github.com/htmlhint/HTMLHint/blob/master/docs/user-guide/usage/options.md

However the negation command '!' is currently useless.

This means if I only want to search in a folder, I can't use

!**/GoodFolder/**

Instead I must manually ignore all other folders.

**/BadFolder1/**,......,**/BadFolder8889986767/**

I'd also be ok if you allowed a new rule that would filter paths that could be modified in .htmlhintrc

[woodconn]

Workaround, I found this to work as expected, however I don't know if I can feed it multiple paths like ignore is capable of:
Run npx htmlhint "**/GoodFolder/**/*.razor"

[hyperupcall]

The glob package mentions that negation was removed in v6. HTMLHint currently uses glob v8.

globby supportgs negation, but I am not convinced it is worth switching. The user can supply multiple glob patterns as regular arguments to htmlhint. Furthermore, @babel/cli, npm, mocha, tslint, browserify, grunt, styelus, nyc, karma, etc. all use glob, so I think the user experience could be improved without changing how --ignored globs are parsed