feat: add disclosure button (resolves #150)

[greatislander]

• I've read the guidelines for Contributing to the Platform Co-op Toolkit
• This isn't a duplicate of an existing pull request

Description

Adds disclosure button component.

Steps to test

Review component:

• https://deploy-preview-154--pinecone.netlify.com/components/preview/disclosure-button.html

Additional information

Not applicable.

Related issues

• Resolves Atom: disclosure button #150.

[jhung]

I was reviewing this component and I realized that depending on the context, it is semantically better to use the native <summary><details> pattern instead of a button with Javascript. Summary-details would make sense for some of the text content such as notifications and paragraph text.

See https://developer.mozilla.org/en-US/docs/Web/HTML/Element/details

Summary-Details should not be used in cases like the sidebar navigation - semantically it won't make sense as a parent item is not a summary of the sub items.

All that said, this disclosure component is still useful, but summary-detailis should be used instead where it is appropriate.

[greatislander]

More notes on <summary> and <details>:

• https://css-tricks.com/quick-reminder-that-details-summary-is-the-easiest-way-ever-to-make-an-accordion/
• https://www.scottohara.me/blog/2018/09/03/details-and-summary.html
• https://adrianroselli.com/2019/04/details-summary-are-not-insert-control-here.html
• https://daverupert.com/2019/12/why-details-is-not-an-accordion/

[greatislander]

@jhung I've merged as-is. It looks like there's some weird workarounds needed to style summary/details the way the designs specify, and it would need to be polyfilled for IE/non-Chromium Edge. Can you create a follow-up issue for this?

[cherylhjli]

Is there a way to bump the up chevron arrow down a little bit, or would that affect the down chevron as well?

[greatislander]

It would affect the down chevron as well and if the vertical positioning changed between states the rotation would look weird (it would shift up/down while rotating).

[cherylhjli]

ok, don't worry about it then! it works as it is