Add support for tel: links

[mrk-j]

When merged this PR adds support for tel: links. We came across this 'issue' when using spatie/menu.

I hope you can merge this! Thank you 🦾

[freekmurze]

I think it makes sense to merge this, but I think it's a breaking change. Some people might now rely on the fact that we throw an exception when we come across a non-http(s) link.

[mrk-j]

True, there is already support for mailto: links in the package. So non-http(s) links are already allowed in some form. How do you want to proceed?

[freekmurze]

Ah indeed! I've check in our package that use this package, and it seems we already check everywhere on the right protocol.

I'm going to assume that our other package users to do this too and consider this a non-breaking change.

Thanks for your work on this! 👍