Add option to choose default protocol when missing

[laurensnl]

Autolinker currently defaults to http when the protocol is missing from the link. Would be neat if we could choose to default to https!

[gregjacobs]

Hey @laurensnl, so sorry for the very late reply on this.

I'm thinking: since we can't predict which sites users are going to autolink to, it may not be a good idea to set an option like this to 'https'. This may end up creating invalid links for sites that are not configured to serve https, and any good site like google/facebook/etc already redirect you from http -> https when you request it. I think we may want to leave it as is, unless you think otherwise? (Maybe there's a use case I'm missing?)

[laurensnl]

Personally, I would prefer to link to the correct (https) domain, especially now the majority of the websites is using https. I'm using your library in a business where all websites that we link to do support https. But you're right: linking to http will probably produce a correct link in more cases.