Class object syntax

[mhanberg]

Allows for conditionally setting classes on an element.

This is similar to Vue.js's Class Bindings - Object Syntax

div class: ["text-red-500": false, "text-green-500": true] do
  @user.name
end

results in

<div class="text-green-500">
  Homer Simpson
</div>

[mhanberg]

Still needs docs