feat: add missing --include flag & linksToInclude option

[marapper]

You have --include flag description in README but part with implementation is kinda missing. As I suppose it should work like same flag in other tooling. Or maybe even like .ignore files - with ! at start of strings.

We need something like that in our small project in which I implement your lib. So I hope it's ok, my accidentaly PRs.

Here the issue #44

[JustinBeckwith]

Thanks for the PR! So to be honest, I'm kind of torn on this one. I'm trying to be a little careful with the number of flags we add. Can you share under what circumstances you'd use something like this?

We've found that having skip and then scanning the whole site generally suits our needs. When would you use something like this?

[marapper]

Yes, I understand your concerns.

But I think exclude flags is not powerful enough without force includes. Thats why all .ignore files and test-properties in tooling have both.

Two simple wxample for crawling:

1. If we want to check all internal links but not externals. So we could skip all links (/.*/) but allow internal links by domain.

2. We can forbid to check all youtube-domain but allow /youtube.com\/watch.*/

Also you already have --include, -i description in README.md

[marapper]

Are you still have doubts?

[JustinBeckwith]

So I think I'm ready to call it - I don't think this is needed. Recently we landed #120, which lets you decide if a link is skipped by passing it through a function. So for sufficiently advanced scenarios, you can drop down to the filter function to really control what comes back.

I'm going to go ahead and close this out for now - but really, thank you for the POC.

[marapper]

Yes, it's totally reasonable. include description in README.md is no longer needed may be