Add option for slide advance/pause buttons on sliders#54

In some sections, like the quotes section for example, it’s there’s no way to reliably resume or advance the slides if it’s been stopped. Would like to add the option to show buttons as part of the interface, to be able to resume/pause or advance the slides.

it seems the buttons are all there just styled off the screen and hidden with css with hte .visually-hidden class. Hoping this is a simplier upgrade that we can see come in a future upgrade as it seems viable since flickity comes with the functionality, why strip it out after all.