Add #killer-use-cases section

[maximveksler]

The general idea is to get people excited by what is possible and is already out there.

• https://joernhees.github.io/associations/
• http://solid.inrupt.com

[amirouche]

Versioned database ala git 💯

[zacharywhitley]

I'm closing this. It's out of scope for an awesome list and if after 20 years of development people still can't find meaningful use cases maybe it wasn't such a good idea after all. Semantic web people need a good smack in the face. There are plenty of use cases. Go figure out why people aren't using it. There are reasons.