Create a demo module to showcase best practices

3.x introduced a new way of creating Facets

We should create a demo module which incorporates all best practices, and can be run on simplytest.me
This demo should use all suggested contrib to create the best user experience.

Features which should be in the demo

- Facets on taxonomy fields, rendered as checkboxes
- Hierarchical date facet
- Hierarchical taxonomy facet
- Default content
- Ajax and views_ajax_history default enabled
- views summary for facets and search string

For now, let's focus on a demo for "Facets exposed filters"
We can always add a facet block demo later.