Provide config for short urls

[danielmt]

Providing a data-short-url could enhance twitter sharing with big urls, so you could fill both data-url and data-short-url and depending on the service, it would pick the latter.

[orafaelfragoso]

@danielmt As of 2017 we already have automatic url shortening on Twitter, no reason for that anymore.

https://support.twitter.com/articles/294524