<howto-slider> pt. 2

[robdodson]

@sendilkumarn this PR addresses some changes from #129

Because I wasn't able to push to that PR I had to create a new one.

The main changes I made were to turn ARIA into an implementation detail. So the element exposes value, min, max attributes and properties, and those reflect to ARIA but only as a side effect. Anyone consuming the component should never need to work with ARIA directly (the same way you don't have to work with ARIA when you're using <input type="range>).

I also tried to refactor the code so most things are driven off of setting the value property. So setting the value property triggers the attributeChangedCallback which in turn moves the thumb.

Also note that changing the min or max attributes/properties will set the value equal to itself again. This is useful if you have value=50 and you change min from 0 to 50. The thumb will update and appear at the beginning of the track instead of in the middle.

I think this could use some more work but I think we're getting to a good place :)

[googlebot]

So there's good news and bad news.

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[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored by someone other than the pull request submitter. We need to confirm that all authors are ok with their commits being contributed to this project. Please have them confirm that here in the pull request.

Note to project maintainer: This is a terminal state, meaning the cla/google commit status will not change from this State. It's up to you to confirm consent of the commit author(s) and merge this pull request when appropriate.

[robdodson]

Oh also I removed the label from the shadow dom because <input type="range"> doesn't have a built-in label. I realize they use one in the ARIA Authoring Practices example but I wanted to try to simplify the code as much as possible.

[sendilkumarn]

@robdodson 👍 anything else has to be done over here

[robdodson]

I think it's nearly done, sorry for the delay, the holidays got in the way. I'm back in the office this week and hopefully can wrap it up.