Add an autoplay attribute to the `tp-slider`

[benerd]

@junaidbhura - There are scenarios where we don't have any arrows or nav pills to navigate between different slides. Now I am Working on et-immersive-inquiry-form where each slide changes after every 4 seconds, so to implement this I had to wrap our tp-slider inside a custom component so that I can add add a setInterval() on it.
FYR: Markup, JS,

I think it will be great if we can add the autoplay and transition-speed attribute, and then if the autoplay="yes" then we will do the below:

setInterval( () => { // Change the slide. this.next(); }, this.getAttribute( 'transition-speed' ) );

LMK your thoughts on this?

[junaidbhura]

Thanks @benerd would you like to pick this up? We can leave the transition speed to CSS

[benerd]

sure @junaidbhura - I am picking it up.

[benerd]

@junaidbhura - here is the PR for this, added an auto-slide-interval attribute as we for the setInterval to change after a certain period of time.